GMC front wheel bearings

C

claude brousson

New member
Jan 20, 1999
292
0
0
It seems to me that the GMC front wheel bearings have over the years
generated more heat than any other area of the vehicle.I think this is
true both literally and figuratively.
I recall that in the past,one of the original GM mechanics who went back
to GM for training re GMC's, Roland Wilbur, of Oregon ( not sure if he
is alive still or not- if so he'd be about 87 now. Last time I saw him
he was still buying GM buses and having fun and that was about 2-3 years
ago)he used to try various bearings including Hyatt, and Bower. When
doing a bearing he used Amsoil(Sp) grease.However the spacing on his
instalations was much less and would vary from bearing to bearing. I
recall that he found that on the Bower Japanese bearing the spacing
would vary all the way from 4-6000th clearance rather than the now
recomended .0095

At the time he was experimenting with different tolerances, I don't
think GM had sorted out what the best clearance should be. What did
become clear after time was that GMC's were having trouble with their
front wheels. I don't know whether any of Wilburs lower axial clearances
mountings gave trouble or not, however GM did eventually address the
problem and now supply a bearing which has specific,written right on the
bearing, axial clearance of .0095" . They also are rated to carry 20%
more load bearing capability. Do other generic or other brands have this
capability? Who knows. Likely short of testing in the lab, it will never
be proven. I don't even think that other bearings will test with the
same axial clearance from bearing to bearing, as do the OEM ones suppied
from Cinnabar.

One other thing is also a fact and that is many GMC owners are very
educated,opinionated and also just love to explore all the parameters of
fact ,fiction, myth, and a few other things as well. Thats what keeps us
all young and keeps the grey matter working in our heads.

So my suggestion is that the skeptics should all go out and put other
bearings in their vehicles and keep a record of kind, mileage, grease
used, etc. Then they could report back to the rest of us the results.

Ahead of time I would like to wager them -a fully inflated air bag with
hot air,- the following results--
- -A fair number will sooner or later have a bearing failure.
- - It will likely happen out on a desert highway when the temp is about
120 degrees and the air conditioner has already just quit.
- -Your cell phone will likely not be working.
- -Your wife when she learns the truth of what you had done will threaten
divorce calling you a complete idiot. Of course some guys do report
their wives are very understanding, So these will be an exception.
- -The towing bill will be the best part of $500.00
- -By getting the cheaper bearing, you saved at the time of purchase
perhaps 5-10 dollars over the OEM one.

Now on the lighter side, in case some have not heard the GMC joke-

Quite some time back one of the GMC wives was talking to another GMCer-
bemoaning the fact that her husband had a mistress. She didn't know what
to do about it as that was where he was spending all his time and money.
She was a bit philosophical about it though saying at least she knew
where she could always find him as at least when he was with his
mistress he was always either on top of her, inside her or underneith
her, having fun!

Claude in Victoria,BC
 
I'm reading a lot about bearings. Also, I'm hearing 0.0095" axial float for
clearance. That's a lot. Since both or all components (hub, bearing,
housing, etc.) are of similar metal composition they will expand ~the same;
( 6.3 X 10^-6). The axial distance the cover is ~the same or close to the
diameter of the bearing. All deltas can be multiplied by the linear
expansion constant (temp & distance). One can also graphically depict or
project the wobble at tire radius. 9.5 mils over 2 inches would become 95
mils over 20 inches. This equates to ~3/32" and is very bad. Will lead to
premature tire failure and cause wobble. At operating temp I would not
recommend over 3 mils clearance (0.003 inch). Depending on the ABEC spec
which determines internal clearance, I personally prefer 0.001".

And, although temperature is also a predictive parameter, I prefer
accelerometers and magnitude analysis. Vibration data through FFT analysis
provides far greater exhaustive information with much greater accuracy in
diagnosis. Has anyone considered the piezoelectric accelerometer or eddy
current probe for their diagnostic panel? Just a thought. Acquiring data is
one thing; diagnosis is another. Depending on who the analyst is one may be
better off with idiot lights! Generally speaking, the motor home is a
preventive maintenance item rather than a predictive maintenance item. It's
kinda like the lubrication thing: $10/qt oil sees the same ring blow by as
the $1.50 oil. The $10/qt oil may not suffer the same degradation but will
see the same contamination. Solution, change oil often - say, 2kmi.

I'm a consulting engineer specializing in bearing analysis, alignment and
balancing. Lubrication plays a hand in all these. And, there is no
substitute for good lubrication.
I have but one request after being on this thread for two years. These past
two years have resulted in doubling of the mail. Real issues are good, but,
please directly E-mail specifics to a specific person to their personal
E-mail address. Amen. I've been guilty from time to time. But, this isn't a
posting board for personal messages. This might keep some of us from
subscribing and unsubscribing all the time. Just food for thought, not
wanting to stir up a stink or to add to the long list of E-mail. I like
this thread and have profited from it. I think many may feel as I. Your not
responding is appreciated. Thank you.

With best regards; I'm
Sincerely,
Sam Pickens
picksam
 
I really do not want to start another controversey but here goes anyway.

Sam I would like to answer both your message and an earlier one by Brent
since they are of similar content.
Both contain information that I disagree with.

As a professonal engineer, and former Metrologist, I have a tendency to over
engineer everything I do. But in the case of the GMC front wheel bearings I
am satisfied that there are no problems if they are serviced with the
correct bearings, greased correctly, and assembled in within tolerance hubs
and knuckles, and lastly pressed on the hub in the correct manner. Past
attempts at redesigning the hubs and kuckles such as the wallace hub, in my
opinion resulted in expensive parts and a WEAKENED suspension.

I have to say up front however that I have a pet peeve and that is seeing
engineering data that is masquerading as pertaining to the GMC motorhome
when in fact it does not. Sam both your comments and Brents for the most
part are not relevent to the GMC front wheel bearings and their failure or
fitting. The bearings, hubs, and knuckles are trouble free.

In the case of brents remarks about the front wheel bearings he is
incorrect,they are in fact a special bearing(hand etched with the axial
clearance) even though they may appear to have the very same part numbers as
a off the shelf Timken bearing. The correct GM front wheel bearing set is
fitted with a spacer (no two are alike in my experience) such that the axial
clearance is held to .0095". Why that clearance? Because General Motors
Service Parts Operations Engineers (GMSPOE) did extensive tests and analysis
of the many failures of early GMC motorhomes in 1989-90 and concluded that
in a worse case scenario of a (small inside bearing diameter and largest
tolerance hub(2.0020")) that the assembled axial clearance was reduced by as
much as .007". They therefore had Timken design a new front wheel bearng
set that had .0095" of axial clearance and 20% more load bearing capacity.
And yes it is possible to have a similarly looking roller bearing with this
increased load bearing capacity. How? Tighter tolerances, maybe diffent cone
angles and thus longer rollers. I really have not compared the standard
bearing with the new ones to see how they did it.

Lets get to the bottom line on all of this since that is what most netters
want. We have beat this front wheel bearing problem to death and concluded
long ago that there was nothing wrong with the GM system. Install the
correct bearings, pack them correctly, use in tolerance hubs and knuckles,
and you will have a trouble free hub. Don't do it and you are going to have
trouble. The choice as Arch says is yours. Want to break down on the road
far from home with a bad bearing? Than follow some of the alternative advice
I have seen in the last couple of days.

=========
Skip

Thats EXACTLY the info I needed.

This is by no means a special bearing. There are still a couple puzzling
questions, not least of which is why they would fail at low mileages!
Something is horribly amiss here- that bearing isnt working very hard at all
in a GMC. Its considerably understressed. I have some theories I'll bounce
off engineering.

Perhaps the press fit is too tight- the bearing and knuckle have a similar
coefficient of expansion, hence the interference fit should stay pretty
constant. However, material yeilds mean that the bearings cant possibly be
fitted at any greater interference fit than about 0.004" maximum. You
certainly could try, but in no time the materials would ease back to around
that anyhow. If they are installed much too tight in the beginning, and then
materials move and expand, there go the clearances!

Maybe EP 80-90 would be a better lube for these, it would permit preloading
the bearing with a crush sleeve instead of a spacer. No play! The reason
this has occured to me, is I am pretty sure one of those Part Numbers is a
pinion bearing in a GM differential...We sell little automatic lubricators
for things like sawmill machines, one could easily be adapted for this
purpose likely. Even a piece of narrow hose with a wick in it up to the
engine compartment might suffice..

0.0095 clearance IS a LOT. 0.002 is usual on similar bearings on rear
wheels. Typically 0.001"-0.006" is more usual.

Last but not least, I seriously wonder how it could be possible to mail
order a pair of bearings with a spacer withing five/tenTHOUSANDTHS of an
inch precision. That just cant be right!

Curiouser and curiouser. I'll get the smart guys to look at this for us,
they'll know!

Brent Covey
Vancouver

> -Information on the inner race in order: Timken,.1209 (etched by
>hand),LM104949E,+,USA AL.

=====================================

>I'm reading a lot about bearings. Also, I'm hearing 0.0095" axial float for
>clearance. That's a lot. Since both or all components (hub, bearing,
>housing, etc.) are of similar metal composition they will expand ~the same;
>( 6.3 X 10^-6). The axial distance the cover is ~the same or close to the
>diameter of the bearing. All deltas can be multiplied by the linear
>expansion constant (temp & distance). One can also graphically depict or
>project the wobble at tire radius. 9.5 mils over 2 inches would become 95
>mils over 20 inches. This equates to ~3/32" and is very bad. Will lead to
>premature tire failure and cause wobble. At operating temp I would not
>recommend over 3 mils clearance (0.003 inch). Depending on the ABEC spec
>which determines internal clearance, I personally prefer 0.001".
>
>And, although temperature is also a predictive parameter, I prefer
>accelerometers and magnitude analysis. Vibration data through FFT analysis
>provides far greater exhaustive information with much greater accuracy in
>diagnosis. Has anyone considered the piezoelectric accelerometer or eddy
>current probe for their diagnostic panel? Just a thought. Acquiring data is
>one thing; diagnosis is another. Depending on who the analyst is one may be
>better off with idiot lights! Generally speaking, the motor home is a
>preventive maintenance item rather than a predictive maintenance item. It's
>kinda like the lubrication thing: $10/qt oil sees the same ring blow by as
>the $1.50 oil. The $10/qt oil may not suffer the same degradation but will
>see the same contamination. Solution, change oil often - say, 2kmi.
>
>I'm a consulting engineer specializing in bearing analysis, alignment and
>balancing. Lubrication plays a hand in all these. And, there is no
>substitute for good lubrication.
>I have but one request after being on this thread for two years. These past
>two years have resulted in doubling of the mail. Real issues are good, but,
>please directly E-mail specifics to a specific person to their personal
>E-mail address. Amen. I've been guilty from time to time. But, this isn't a
>posting board for personal messages. This might keep some of us from
>subscribing and unsubscribing all the time. Just food for thought, not
>wanting to stir up a stink or to add to the long list of E-mail. I like
>this thread and have profited from it. I think many may feel as I. Your not
>responding is appreciated. Thank you.
>
>With best regards; I'm
>Sincerely,
>Sam Pickens
>picksam
>
>
>
 
Tom,
I hope one of our treasured website people (Patrick or Gene) will make your
informative statements available to all those who in the future will again bring
up the front bearing failure subject.
Gary
North Bend, Oregon Coast

> I really do not want to start another controversey but here goes anyway.
>
> Sam I would like to answer both your message and an earlier one by Brent
> since they are of similar content.
> Both contain information that I disagree with.
>
> As a professonal engineer, and former Metrologist, I have a tendency to over
> engineer everything I do. But in the case of the GMC front wheel bearings I
> am satisfied that there are no problems if they are serviced with the
> correct bearings, greased correctly, and assembled in within tolerance hubs
> and knuckles, and lastly pressed on the hub in the correct manner. Past
> attempts at redesigning the hubs and kuckles such as the wallace hub, in my
> opinion resulted in expensive parts and a WEAKENED suspension.
>
> I have to say up front however that I have a pet peeve and that is seeing
> engineering data that is masquerading as pertaining to the GMC motorhome
> when in fact it does not. Sam both your comments and Brents for the most
> part are not relevent to the GMC front wheel bearings and their failure or
> fitting. The bearings, hubs, and knuckles are trouble free.
>
> In the case of brents remarks about the front wheel bearings he is
> incorrect,they are in fact a special bearing(hand etched with the axial
> clearance) even though they may appear to have the very same part numbers as
> a off the shelf Timken bearing. The correct GM front wheel bearing set is
> fitted with a spacer (no two are alike in my experience) such that the axial
> clearance is held to .0095". Why that clearance? Because General Motors
> Service Parts Operations Engineers (GMSPOE) did extensive tests and analysis
> of the many failures of early GMC motorhomes in 1989-90 and concluded that
> in a worse case scenario of a (small inside bearing diameter and largest
> tolerance hub(2.0020")) that the assembled axial clearance was reduced by as
> much as .007". They therefore had Timken design a new front wheel bearng
> set that had .0095" of axial clearance and 20% more load bearing capacity.
> And yes it is possible to have a similarly looking roller bearing with this
> increased load bearing capacity. How? Tighter tolerances, maybe diffent cone
> angles and thus longer rollers. I really have not compared the standard
> bearing with the new ones to see how they did it.
>
> Lets get to the bottom line on all of this since that is what most netters
> want. We have beat this front wheel bearing problem to death and concluded
> long ago that there was nothing wrong with the GM system. Install the
> correct bearings, pack them correctly, use in tolerance hubs and knuckles,
> and you will have a trouble free hub. Don't do it and you are going to have
> trouble. The choice as Arch says is yours. Want to break down on the road
> far from home with a bad bearing? Than follow some of the alternative advice
> I have seen in the last couple of days.
>
> =========
> Skip
>
> Thats EXACTLY the info I needed.
>
> This is by no means a special bearing. There are still a couple puzzling
> questions, not least of which is why they would fail at low mileages!
> Something is horribly amiss here- that bearing isnt working very hard at all
> in a GMC. Its considerably understressed. I have some theories I'll bounce
> off engineering.
>
> Perhaps the press fit is too tight- the bearing and knuckle have a similar
> coefficient of expansion, hence the interference fit should stay pretty
> constant. However, material yeilds mean that the bearings cant possibly be
> fitted at any greater interference fit than about 0.004" maximum. You
> certainly could try, but in no time the materials would ease back to around
> that anyhow. If they are installed much too tight in the beginning, and then
> materials move and expand, there go the clearances!
>
> Maybe EP 80-90 would be a better lube for these, it would permit preloading
> the bearing with a crush sleeve instead of a spacer. No play! The reason
> this has occured to me, is I am pretty sure one of those Part Numbers is a
> pinion bearing in a GM differential...We sell little automatic lubricators
> for things like sawmill machines, one could easily be adapted for this
> purpose likely. Even a piece of narrow hose with a wick in it up to the
> engine compartment might suffice..
>
> 0.0095 clearance IS a LOT. 0.002 is usual on similar bearings on rear
> wheels. Typically 0.001"-0.006" is more usual.
>
> Last but not least, I seriously wonder how it could be possible to mail
> order a pair of bearings with a spacer withing five/tenTHOUSANDTHS of an
> inch precision. That just cant be right!
>
> Curiouser and curiouser. I'll get the smart guys to look at this for us,
> they'll know!
>
> Brent Covey
> Vancouver
>
> > -Information on the inner race in order: Timken,.1209 (etched by
> >hand),LM104949E,+,USA AL.
>
> =====================================

> >I'm reading a lot about bearings. Also, I'm hearing 0.0095" axial float for
> >clearance. That's a lot. Since both or all components (hub, bearing,
> >housing, etc.) are of similar metal composition they will expand ~the same;
> >( 6.3 X 10^-6). The axial distance the cover is ~the same or close to the
> >diameter of the bearing. All deltas can be multiplied by the linear
> >expansion constant (temp & distance). One can also graphically depict or
> >project the wobble at tire radius. 9.5 mils over 2 inches would become 95
> >mils over 20 inches. This equates to ~3/32" and is very bad. Will lead to
> >premature tire failure and cause wobble. At operating temp I would not
> >recommend over 3 mils clearance (0.003 inch). Depending on the ABEC spec
> >which determines internal clearance, I personally prefer 0.001".
> >
> >And, although temperature is also a predictive parameter, I prefer
> >accelerometers and magnitude analysis. Vibration data through FFT analysis
> >provides far greater exhaustive information with much greater accuracy in
> >diagnosis. Has anyone considered the piezoelectric accelerometer or eddy
> >current probe for their diagnostic panel? Just a thought. Acquiring data is
> >one thing; diagnosis is another. Depending on who the analyst is one may be
> >better off with idiot lights! Generally speaking, the motor home is a
> >preventive maintenance item rather than a predictive maintenance item. It's
> >kinda like the lubrication thing: $10/qt oil sees the same ring blow by as
> >the $1.50 oil. The $10/qt oil may not suffer the same degradation but will
> >see the same contamination. Solution, change oil often - say, 2kmi.
> >
> >I'm a consulting engineer specializing in bearing analysis, alignment and
> >balancing. Lubrication plays a hand in all these. And, there is no
> >substitute for good lubrication.
> >I have but one request after being on this thread for two years. These past
> >two years have resulted in doubling of the mail. Real issues are good, but,
> >please directly E-mail specifics to a specific person to their personal
> >E-mail address. Amen. I've been guilty from time to time. But, this isn't a
> >posting board for personal messages. This might keep some of us from
> >subscribing and unsubscribing all the time. Just food for thought, not
> >wanting to stir up a stink or to add to the long list of E-mail. I like
> >this thread and have profited from it. I think many may feel as I. Your not
> >responding is appreciated. Thank you.
> >
> >With best regards; I'm
> >Sincerely,
> >Sam Pickens
> >picksam
> >
> >
> >
 
Oh Arch loosen your panty girdle and relax, and put the gloves back on or
whatever. Why would I want to use your name to support any thing I say. That
would be a kin to trying to transport the space shuttle on a cessna air
plane. Get a hold of yourself. I am starting to think that you are in to the
fermented juice late at night! On second thought maybe that is a good idea
and I am going for a double scotch before finishing this.

I never said that GM nor Timkin took run of the mill bearings and made
adjustments to them. Some one else did. Read the June 1996 issue of the GMC
Motorhome News page 7 for gods sake instead of this incessant rantings and
ravings you seem to prefer. Its time to be constructive. Do you want to kill
the myths or go down in history as the last one that supports them/

I remember a favorite saying of my grandfather Arch "If you want to switch
horses in midstream, make sure both of them are going the same way"..Good
advice Arch. Get on board.

DISCLAIMER: NONE OF THE INFORMATION THAT I POST OR WILL POST IS ENDORSED OR
SUPPORTED BY PROFESSOR ARCHER. HE SUPPORTS HIS OWN MYTHS.

STill Peace

>In a message dated 9/6/99 8:10:20 PM Central Daylight Time, warner
>writes:
>
>> The choice as Arch says is yours. Want to break down on the road
>> far from home with a bad bearing? Than follow some of the alternative
>advice
>> I have seen in the last couple of days.
>>
>tom
>
>Damn man you keep using this. Now when I cried uncle it was my
>understanding that Timken took the run of the mill bearing and made
>some adjustments to it. Now you are saying they redesigned the bearing
>NO WAY!! I think it was Henry or Heinz that sealed my coffin on that
>fight. I would sure like to hear from them on your new claim that the
>bearing was redesigned. DONT put my name on your rantings! I dont
>agree with you on a lot of things. I told you at the time that if you
>stayed out of my face I would not be in yours. I have seen several
>post by you that I disagree with but I have said nothing. Now
>you try to use my name to support your ideas. The gloves are off.
>
>Take Care
>Arch
>
>
 
Arch and Tom
Let's not get into it again. This time you'll both be sent to your rooms WITHOUT
your computers!!

Mikeb
 
It's archived at http://www.web-access.net/~bmassey/twarner.html under a
letter of 5-7-99.

bdub
Deep in the Heart o Texas

>Tom,
>I hope one of our treasured website people (Patrick or Gene) will make your
>informative statements available to all those who in the future will again
>bring
>up the front bearing failure subject.
>Gary
>North Bend, Oregon Coast
>

>
> > I really do not want to start another controversey but here goes anyway.
> >
> > Sam I would like to answer both your message and an earlier one by Brent
> > since they are of similar content.
> > Both contain information that I disagree with.
> >
> > As a professonal engineer, and former Metrologist, I have a tendency to
> over
> > engineer everything I do. But in the case of the GMC front wheel bearings I
> > am satisfied that there are no problems if they are serviced with the
> > correct bearings, greased correctly, and assembled in within tolerance hubs
> > and knuckles, and lastly pressed on the hub in the correct manner. Past
> > attempts at redesigning the hubs and kuckles such as the wallace hub, in my
> > opinion resulted in expensive parts and a WEAKENED suspension.
> >
> > I have to say up front however that I have a pet peeve and that is seeing
> > engineering data that is masquerading as pertaining to the GMC motorhome
> > when in fact it does not. Sam both your comments and Brents for the most
> > part are not relevent to the GMC front wheel bearings and their failure or
> > fitting. The bearings, hubs, and knuckles are trouble free.
> >
> > In the case of brents remarks about the front wheel bearings he is
> > incorrect,they are in fact a special bearing(hand etched with the axial
> > clearance) even though they may appear to have the very same part
> numbers as
> > a off the shelf Timken bearing. The correct GM front wheel bearing set is
> > fitted with a spacer (no two are alike in my experience) such that the
> axial
> > clearance is held to .0095". Why that clearance? Because General Motors
> > Service Parts Operations Engineers (GMSPOE) did extensive tests and
> analysis
> > of the many failures of early GMC motorhomes in 1989-90 and concluded that
> > in a worse case scenario of a (small inside bearing diameter and largest
> > tolerance hub(2.0020")) that the assembled axial clearance was reduced
> by as
> > much as .007". They therefore had Timken design a new front wheel bearng
> > set that had .0095" of axial clearance and 20% more load bearing capacity.
> > And yes it is possible to have a similarly looking roller bearing with this
> > increased load bearing capacity. How? Tighter tolerances, maybe diffent
> cone
> > angles and thus longer rollers. I really have not compared the standard
> > bearing with the new ones to see how they did it.
> >
> > Lets get to the bottom line on all of this since that is what most netters
> > want. We have beat this front wheel bearing problem to death and concluded
> > long ago that there was nothing wrong with the GM system. Install the
> > correct bearings, pack them correctly, use in tolerance hubs and knuckles,
> > and you will have a trouble free hub. Don't do it and you are going to
> have
> > trouble. The choice as Arch says is yours. Want to break down on the road
> > far from home with a bad bearing? Than follow some of the alternative
> advice
> > I have seen in the last couple of days.
> >
> > =========
> > Skip
> >
> > Thats EXACTLY the info I needed.
> >
> > This is by no means a special bearing. There are still a couple puzzling
> > questions, not least of which is why they would fail at low mileages!
> > Something is horribly amiss here- that bearing isnt working very hard
> at all
> > in a GMC. Its considerably understressed. I have some theories I'll bounce
> > off engineering.
> >
> > Perhaps the press fit is too tight- the bearing and knuckle have a similar
> > coefficient of expansion, hence the interference fit should stay pretty
> > constant. However, material yeilds mean that the bearings cant possibly be
> > fitted at any greater interference fit than about 0.004" maximum. You
> > certainly could try, but in no time the materials would ease back to around
> > that anyhow. If they are installed much too tight in the beginning, and
> then
> > materials move and expand, there go the clearances!
> >
> > Maybe EP 80-90 would be a better lube for these, it would permit preloading
> > the bearing with a crush sleeve instead of a spacer. No play! The reason
> > this has occured to me, is I am pretty sure one of those Part Numbers is a
> > pinion bearing in a GM differential...We sell little automatic lubricators
> > for things like sawmill machines, one could easily be adapted for this
> > purpose likely. Even a piece of narrow hose with a wick in it up to the
> > engine compartment might suffice..
> >
> > 0.0095 clearance IS a LOT. 0.002 is usual on similar bearings on rear
> > wheels. Typically 0.001"-0.006" is more usual.
> >
> > Last but not least, I seriously wonder how it could be possible to mail
> > order a pair of bearings with a spacer withing five/tenTHOUSANDTHS of an
> > inch precision. That just cant be right!
> >
> > Curiouser and curiouser. I'll get the smart guys to look at this for us,
> > they'll know!
> >
> > Brent Covey
> > Vancouver
> >
> > > -Information on the inner race in order: Timken,.1209 (etched by
> > >hand),LM104949E,+,USA AL.
> >
> > =====================================

> > >I'm reading a lot about bearings. Also, I'm hearing 0.0095" axial
> float for
> > >clearance. That's a lot. Since both or all components (hub, bearing,
> > >housing, etc.) are of similar metal composition they will expand ~the
> same;
> > >( 6.3 X 10^-6). The axial distance the cover is ~the same or close to the
> > >diameter of the bearing. All deltas can be multiplied by the linear
> > >expansion constant (temp & distance). One can also graphically depict or
> > >project the wobble at tire radius. 9.5 mils over 2 inches would become 95
> > >mils over 20 inches. This equates to ~3/32" and is very bad. Will lead to
> > >premature tire failure and cause wobble. At operating temp I would not
> > >recommend over 3 mils clearance (0.003 inch). Depending on the ABEC spec
> > >which determines internal clearance, I personally prefer 0.001".
> > >
> > >And, although temperature is also a predictive parameter, I prefer
> > >accelerometers and magnitude analysis. Vibration data through FFT analysis
> > >provides far greater exhaustive information with much greater accuracy in
> > >diagnosis. Has anyone considered the piezoelectric accelerometer or eddy
> > >current probe for their diagnostic panel? Just a thought. Acquiring
> data is
> > >one thing; diagnosis is another. Depending on who the analyst is one
> may be
> > >better off with idiot lights! Generally speaking, the motor home is a
> > >preventive maintenance item rather than a predictive maintenance item.
> It's
> > >kinda like the lubrication thing: $10/qt oil sees the same ring blow by as
> > >the $1.50 oil. The $10/qt oil may not suffer the same degradation but will
> > >see the same contamination. Solution, change oil often - say, 2kmi.
> > >
> > >I'm a consulting engineer specializing in bearing analysis, alignment and
> > >balancing. Lubrication plays a hand in all these. And, there is no
> > >substitute for good lubrication.
> > >I have but one request after being on this thread for two years. These
> past
> > >two years have resulted in doubling of the mail. Real issues are good,
> but,
> > >please directly E-mail specifics to a specific person to their personal
> > >E-mail address. Amen. I've been guilty from time to time. But, this
> isn't a
> > >posting board for personal messages. This might keep some of us from
> > >subscribing and unsubscribing all the time. Just food for thought, not
> > >wanting to stir up a stink or to add to the long list of E-mail. I like
> > >this thread and have profited from it. I think many may feel as I.
> Your not
> > >responding is appreciated. Thank you.
> > >
> > >With best regards; I'm
> > >Sincerely,
> > >Sam Pickens
> > >picksam
> > >
> > >
> > >
>
>
 
Arch and Tom,
This kind of stuff is what makes the net so much fun. But please I hope you are
not taking this stuff too seriously! You are both too good a source of GMC lore to
get mad and leave.

Also, if you do continue in this manner, as Mikeb said, I agree that the GMCNet will
have to send both of you to your rooms WITHOUT your computers!!
Richard Waters '76 PB, Troy, MI

> Arch and Tom
> Let's not get into it again. This time you'll both be sent to your rooms WITHOUT
> your computers!!
>
> Mikeb
 
I don't know about Arch but I am not serious in the least, at least about
his rantings and ravings or his possible imbibing of the sauce. AS for my
observations concerning the front wheel bearings I am deadly serious.
We already had a member of the GMC Heritage Cruisers lose a front wheel due
to faulty bearings. He was not hurt thank god. But if everyone does not
start following the recommended bearing installation procedures and parts
someone will not be so lucky. Contrary to some of our opinions this is a
deadly serious business.

Enough said

peace

>Arch and Tom,
>This kind of stuff is what makes the net so much fun. But please I hope
you are
>not taking this stuff too seriously! You are both too good a source of GMC
lore to
>get mad and leave.
>
>Also, if you do continue in this manner, as Mikeb said, I agree that the
GMCNet will
>have to send both of you to your rooms WITHOUT your computers!!
>Richard Waters '76 PB, Troy, MI
>

>
>> Arch and Tom
>> Let's not get into it again. This time you'll both be sent to your rooms
WITHOUT
>> your computers!!
>>
>> Mikeb
>
>
>
 
Not me re bearings.
I used local bearings in the rear
and I'm almost positive my fronts are off the shelf as well as they were
done on an emergency basis in Quebec City as we were returning from vacation
so long ago :-)

I've been watching the threads on bearings etc. and what I will do for the
fronts is get them from Cinnebar and for the rears I'll get the numbers out
of the partsbook and continue to procur locally.

That's worked for me for 200,000+ miles so I'm not going to mess with it,
just as I'm sticking to 65 pounds in my new Michelin E's on my shiny new
Alcoas.

That's what I'm doing :-)

Heinz

> In a message dated 9/6/99 8:10:20 PM Central Daylight Time,
warner

>
> > The choice as Arch says is yours. Want to break down on the road
> > far from home with a bad bearing? Than follow some of the alternative
> advice
> > I have seen in the last couple of days.
> >
> tom
>
> Damn man you keep using this. Now when I cried uncle it was my
> understanding that Timken took the run of the mill bearing and made
> some adjustments to it. Now you are saying they redesigned the bearing
> NO WAY!! I think it was Henry or Heinz that sealed my coffin on that
> fight. I would sure like to hear from them on your new claim that the
> bearing was redesigned. DONT put my name on your rantings! I dont
> agree with you on a lot of things. I told you at the time that if you
> stayed out of my face I would not be in yours. I have seen several
> post by you that I disagree with but I have said nothing. Now
> you try to use my name to support your ideas. The gloves are off.
>
> Take Care
> Arch
>
>
 
As Ken Thoma said, if the bearing
> show no ware & have same spacing then he knows that they are a good set
> of bearings. Those in the box have not proven to be good yet....may not
> be harden properly, etc.

Hi, Duane, glad someone sees it the way I do...I've stayed quiet on this,
but I'm with Ken Thoma. If a bearing is good, I'd tend to trust it more than
an untried new one. That's how we are with people, isn't it? Don't you want
an experienced doctor with a good track record cutting on you over a brand
new graduate? I guess it's because most of my background is in electronics
where 95% of failures occur at or soon after startup. A bearing that has
50,000 miles on it and still looks good probably is. But I'll admit that I
could be wrong; it happened once a long time ago. Please don't tell anyone
though.

Travis
 
>
> > That's what I'm doing :-)
> >
> And who cares anyway ,Heinz! :)

Probably quite true (teehee)

> I'm just going to http://www.bytedesigns.com/gmc/gmc-cam2.htm t=_self] HREF="http://www.bytedesigns.com/gmc/gmc-cam2.htm">Cam 2[/url] and eat
> popcorn while watching.

Curtain's closed today. Had no time to play. Had to play host to a family
get-together today so I didn't even turn it on :-)

Will be ordering a robot mount tomorrow so that when I get back you'll be
able to have cam control while eating your popcorn.

I'm hoping to be testing my roaming cam on the trip south next week Will be
mounting cam on the dash and hope to transmit to the website in realtime
every 15 or 30 minutes.

Heinz
 
This evening's postings have certainly been entertaining. The bearings topic
has certainly generated some interesting dialog. I still hope that none of
the combatants have taken it too seriously.

At this point I don't really know what to think, except that I better pay
attention to my wheel bearings (and possibility my muffler bearings ).

It would seem that there is no one who really knows the absolute truth
about the relationship between our coaches and their wheel bearings,
except that they have to be paid attention to.

There is the group that is adamant that you have to replace the bearings
every 25,000 miles or suffer bad things. On the other hand, there are those
that say you can run them for a very long time if they are not wearing and
that they just may be better then the ones in the box that are untried. Then
there is another group that says (my neighbor I think is the only member)
that the right and left hubs require different size bearings due to certain
manufacturing irregularities at the plant that did the machining on the
castings.

Pretty heady stuff for this lowly computer salesman.
Richard Waters '76 PB, Troy, MI
- -----
 
Rick,

That would be correct for an unassembled clearance. We're rolling ~600 RPM
or 5 Hz which is very slow. If we look at this particular bearing as having
an L10 of three years; which is to say 24 hrs/day, 7 days/week, 365
days/year. How many rev's is that? Now, equate that to hours of service on
the road. How long will you have to run to achieve that many rev's? by the
way three years is low. Pack the bearings by hand - full and fill the
cavity 75% full. (3600 RPM only 55% full). Improper, inadequate, or
insufficient grease is the biggest problem. Those data I published earlier
are correct. regardless, if I'm analyzing a twelve cylinder jag or a GMC:
I'll set up transducers and run down the road. The proof is in the pudding.
Spectral profile FFT analysis will pinpoint the problem!

It's late; labor day, I'm too far gone and may have a fish on the line in
the OH river.

With best regards; I'm
Sincerely,
Sam Pickens
picksam
 
At the risk of beating this thing to death Dick I will add: The best
bearing is a good, used,correct, for the application, bearing that has been
running well for some time. I would not hesitate to pull a bearing that has
been running well, clean it, repack it and reinstall it with new seals for
another 25K miles. The only time that I would not do that is when I did not
know if the bearing was the correct one or did not know its origin. Than I
would replace it and continue on to remove them every 25K mile and the whole
routine again. Look at it this way. If you have access to a bearing puller
it pays for itself at the first service.you can than remove the bearing
safely and reinstall it as many times as you want. The puller that I am
having made has such close tolerances that there is no slop. The bearing can
be safely pulled since it is pulling on the inner race and not the cages or
outer race.

Peace now hope everyone is playing from the same sheet of music
\

>This evening's postings have certainly been entertaining. The bearings topic
>has certainly generated some interesting dialog. I still hope that none of
>the combatants have taken it too seriously.
>
>At this point I don't really know what to think, except that I better pay
>attention to my wheel bearings (and possibility my muffler bearings ).
>
>It would seem that there is no one who really knows the absolute truth
>about the relationship between our coaches and their wheel bearings,
>except that they have to be paid attention to.
>
>There is the group that is adamant that you have to replace the bearings
>every 25,000 miles or suffer bad things. On the other hand, there are those
>that say you can run them for a very long time if they are not wearing and
>that they just may be better then the ones in the box that are untried. Then
>there is another group that says (my neighbor I think is the only member)
>that the right and left hubs require different size bearings due to certain
>manufacturing irregularities at the plant that did the machining on the
>castings.
>
>Pretty heady stuff for this lowly computer salesman.
>Richard Waters '76 PB, Troy, MI
>-----
>
>
>
>
>
 
Tom, Who cares about controversy its all just an opinion. And hopefully
facts will align and all will track true. But why is the Wallace hub a
WEAKENED suspension? I have the Wallace hubs on my Pumpkin-Rose installed by
P.O. 8-89 with 18,000 miles on them, Which seems to be doing just fine, did
repack before last trip(JT-6), even tho I had 7k left before repack per
P.O., I do travel the highway and byways at higher then normal RV speeds so
says the boss and would just like to get info if hubs are weakened? what
should I look for? Just so if need be I can start saving $ to replace hubs.
But so far with my limited (3000mi.) GMC time all seem to be ok in the
Wallace bearing/hub set Oh yea and rock guard. A wondering mind what's to
know just to keep travel safe and problems down!!

Ron&Gina
73 Pumpkin-Rose
Ft.Mohave,AZ.

- ----- Original Message -----
From:
To:
Sent: Monday, September 06, 1999 6:09 PM
Subject: Re: GMC: GMC front wheel bearings

> I really do not want to start another controversey but here goes anyway.
>
> Sam I would like to answer both your message and an earlier one by Brent
> since they are of similar content.
> Both contain information that I disagree with.
>
> As a professonal engineer, and former Metrologist, I have a tendency to
over
> engineer everything I do. But in the case of the GMC front wheel bearings
I
> am satisfied that there are no problems if they are serviced with the
> correct bearings, greased correctly, and assembled in within tolerance
hubs
> and knuckles, and lastly pressed on the hub in the correct manner. Past
> attempts at redesigning the hubs and kuckles such as the wallace hub, in
my
> opinion resulted in expensive parts and a WEAKENED suspension.
>
> I have to say up front however that I have a pet peeve and that is seeing
> engineering data that is masquerading as pertaining to the GMC motorhome
> when in fact it does not. Sam both your comments and Brents for the most
> part are not relevent to the GMC front wheel bearings and their failure or
> fitting. The bearings, hubs, and knuckles are trouble free.
>
> In the case of brents remarks about the front wheel bearings he is
> incorrect,they are in fact a special bearing(hand etched with the axial
> clearance) even though they may appear to have the very same part numbers
as
> a off the shelf Timken bearing. The correct GM front wheel bearing set is
> fitted with a spacer (no two are alike in my experience) such that the
axial
> clearance is held to .0095". Why that clearance? Because General Motors
> Service Parts Operations Engineers (GMSPOE) did extensive tests and
analysis
> of the many failures of early GMC motorhomes in 1989-90 and concluded that
> in a worse case scenario of a (small inside bearing diameter and largest
> tolerance hub(2.0020")) that the assembled axial clearance was reduced by
as
> much as .007". They therefore had Timken design a new front wheel bearng
> set that had .0095" of axial clearance and 20% more load bearing capacity.
> And yes it is possible to have a similarly looking roller bearing with
this
> increased load bearing capacity. How? Tighter tolerances, maybe diffent
cone
> angles and thus longer rollers. I really have not compared the standard
> bearing with the new ones to see how they did it.
>
>
> Lets get to the bottom line on all of this since that is what most netters
> want. We have beat this front wheel bearing problem to death and concluded
> long ago that there was nothing wrong with the GM system. Install the
> correct bearings, pack them correctly, use in tolerance hubs and knuckles,
> and you will have a trouble free hub. Don't do it and you are going to
have
> trouble. The choice as Arch says is yours. Want to break down on the road
> far from home with a bad bearing? Than follow some of the alternative
advice
> I have seen in the last couple of days.
>
>
>
>
>
>
>
>
>
> =========
> Skip
>
> Thats EXACTLY the info I needed.
>
> This is by no means a special bearing. There are still a couple puzzling
> questions, not least of which is why they would fail at low mileages!
> Something is horribly amiss here- that bearing isnt working very hard at
all
> in a GMC. Its considerably understressed. I have some theories I'll bounce
> off engineering.
>
> Perhaps the press fit is too tight- the bearing and knuckle have a similar
> coefficient of expansion, hence the interference fit should stay pretty
> constant. However, material yeilds mean that the bearings cant possibly be
> fitted at any greater interference fit than about 0.004" maximum. You
> certainly could try, but in no time the materials would ease back to
around
> that anyhow. If they are installed much too tight in the beginning, and
then
> materials move and expand, there go the clearances!
>
> Maybe EP 80-90 would be a better lube for these, it would permit
preloading
> the bearing with a crush sleeve instead of a spacer. No play! The reason
> this has occured to me, is I am pretty sure one of those Part Numbers is a
> pinion bearing in a GM differential...We sell little automatic lubricators
> for things like sawmill machines, one could easily be adapted for this
> purpose likely. Even a piece of narrow hose with a wick in it up to the
> engine compartment might suffice..
>
> 0.0095 clearance IS a LOT. 0.002 is usual on similar bearings on rear
> wheels. Typically 0.001"-0.006" is more usual.
>
> Last but not least, I seriously wonder how it could be possible to mail
> order a pair of bearings with a spacer withing five/tenTHOUSANDTHS of an
> inch precision. That just cant be right!
>
> Curiouser and curiouser. I'll get the smart guys to look at this for us,
> they'll know!
>
> Brent Covey
> Vancouver
>
>
>
>
> > -Information on the inner race in order: Timken,.1209 (etched by
> >hand),LM104949E,+,USA AL.
>
>
> =====================================

> >I'm reading a lot about bearings. Also, I'm hearing 0.0095" axial float
for
> >clearance. That's a lot. Since both or all components (hub, bearing,
> >housing, etc.) are of similar metal composition they will expand ~the
same;
> >( 6.3 X 10^-6). The axial distance the cover is ~the same or close to the
> >diameter of the bearing. All deltas can be multiplied by the linear
> >expansion constant (temp & distance). One can also graphically depict or
> >project the wobble at tire radius. 9.5 mils over 2 inches would become 95
> >mils over 20 inches. This equates to ~3/32" and is very bad. Will lead to
> >premature tire failure and cause wobble. At operating temp I would not
> >recommend over 3 mils clearance (0.003 inch). Depending on the ABEC spec
> >which determines internal clearance, I personally prefer 0.001".
> >
> >And, although temperature is also a predictive parameter, I prefer
> >accelerometers and magnitude analysis. Vibration data through FFT
analysis
> >provides far greater exhaustive information with much greater accuracy in
> >diagnosis. Has anyone considered the piezoelectric accelerometer or eddy
> >current probe for their diagnostic panel? Just a thought. Acquiring data
is
> >one thing; diagnosis is another. Depending on who the analyst is one may
be
> >better off with idiot lights! Generally speaking, the motor home is a
> >preventive maintenance item rather than a predictive maintenance item.
It's
> >kinda like the lubrication thing: $10/qt oil sees the same ring blow by
as
> >the $1.50 oil. The $10/qt oil may not suffer the same degradation but
will
> >see the same contamination. Solution, change oil often - say, 2kmi.
> >
> >I'm a consulting engineer specializing in bearing analysis, alignment and
> >balancing. Lubrication plays a hand in all these. And, there is no
> >substitute for good lubrication.
> >I have but one request after being on this thread for two years. These
past
> >two years have resulted in doubling of the mail. Real issues are good,
but,
> >please directly E-mail specifics to a specific person to their personal
> >E-mail address. Amen. I've been guilty from time to time. But, this isn't
a
> >posting board for personal messages. This might keep some of us from
> >subscribing and unsubscribing all the time. Just food for thought, not
> >wanting to stir up a stink or to add to the long list of E-mail. I like
> >this thread and have profited from it. I think many may feel as I. Your
not
> >responding is appreciated. Thank you.
> >
> >With best regards; I'm
> >Sincerely,
> >Sam Pickens
> >picksam
> >
> >
> >
>
 
In my opinion the wallace hub weakens the knuckle since it has to be
machined for the third bearing.

>Tom, Who cares about controversy its all just an opinion. And hopefully
>facts will align and all will track true. But why is the Wallace hub a
>WEAKENED suspension? I have the Wallace hubs on my Pumpkin-Rose installed by
>P.O. 8-89 with 18,000 miles on them, Which seems to be doing just fine, did
>repack before last trip(JT-6), even tho I had 7k left before repack per
>P.O., I do travel the highway and byways at higher then normal RV speeds so
>says the boss and would just like to get info if hubs are weakened? what
>should I look for? Just so if need be I can start saving $ to replace hubs.
>But so far with my limited (3000mi.) GMC time all seem to be ok in the
>Wallace bearing/hub set Oh yea and rock guard. A wondering mind what's to
>know just to keep travel safe and problems down!!
>
>Ron&Gina
>73 Pumpkin-Rose
>Ft.Mohave,AZ.
>
>----- Original Message -----
>From:
>To:
>Sent: Monday, September 06, 1999 6:09 PM
>Subject: Re: GMC: GMC front wheel bearings
>
>
>> I really do not want to start another controversey but here goes anyway.
>>
>> Sam I would like to answer both your message and an earlier one by Brent
>> since they are of similar content.
>> Both contain information that I disagree with.
>>
>> As a professonal engineer, and former Metrologist, I have a tendency to
>over
>> engineer everything I do. But in the case of the GMC front wheel bearings
>I
>> am satisfied that there are no problems if they are serviced with the
>> correct bearings, greased correctly, and assembled in within tolerance
>hubs
>> and knuckles, and lastly pressed on the hub in the correct manner. Past
>> attempts at redesigning the hubs and kuckles such as the wallace hub, in
>my
>> opinion resulted in expensive parts and a WEAKENED suspension.
>>
>> I have to say up front however that I have a pet peeve and that is seeing
>> engineering data that is masquerading as pertaining to the GMC motorhome
>> when in fact it does not. Sam both your comments and Brents for the most
>> part are not relevent to the GMC front wheel bearings and their failure or
>> fitting. The bearings, hubs, and knuckles are trouble free.
>>
>> In the case of brents remarks about the front wheel bearings he is
>> incorrect,they are in fact a special bearing(hand etched with the axial
>> clearance) even though they may appear to have the very same part numbers
>as
>> a off the shelf Timken bearing. The correct GM front wheel bearing set is
>> fitted with a spacer (no two are alike in my experience) such that the
>axial
>> clearance is held to .0095". Why that clearance? Because General Motors
>> Service Parts Operations Engineers (GMSPOE) did extensive tests and
>analysis
>> of the many failures of early GMC motorhomes in 1989-90 and concluded that
>> in a worse case scenario of a (small inside bearing diameter and largest
>> tolerance hub(2.0020")) that the assembled axial clearance was reduced by
>as
>> much as .007". They therefore had Timken design a new front wheel bearng
>> set that had .0095" of axial clearance and 20% more load bearing capacity.
>> And yes it is possible to have a similarly looking roller bearing with
>this
>> increased load bearing capacity. How? Tighter tolerances, maybe diffent
>cone
>> angles and thus longer rollers. I really have not compared the standard
>> bearing with the new ones to see how they did it.
>>
>>
>> Lets get to the bottom line on all of this since that is what most netters
>> want. We have beat this front wheel bearing problem to death and concluded
>> long ago that there was nothing wrong with the GM system. Install the
>> correct bearings, pack them correctly, use in tolerance hubs and knuckles,
>> and you will have a trouble free hub. Don't do it and you are going to
>have
>> trouble. The choice as Arch says is yours. Want to break down on the road
>> far from home with a bad bearing? Than follow some of the alternative
>advice
>> I have seen in the last couple of days.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> =========
>> Skip
>>
>> Thats EXACTLY the info I needed.
>>
>> This is by no means a special bearing. There are still a couple puzzling
>> questions, not least of which is why they would fail at low mileages!
>> Something is horribly amiss here- that bearing isnt working very hard at
>all
>> in a GMC. Its considerably understressed. I have some theories I'll bounce
>> off engineering.
>>
>> Perhaps the press fit is too tight- the bearing and knuckle have a similar
>> coefficient of expansion, hence the interference fit should stay pretty
>> constant. However, material yeilds mean that the bearings cant possibly be
>> fitted at any greater interference fit than about 0.004" maximum. You
>> certainly could try, but in no time the materials would ease back to
>around
>> that anyhow. If they are installed much too tight in the beginning, and
>then
>> materials move and expand, there go the clearances!
>>
>> Maybe EP 80-90 would be a better lube for these, it would permit
>preloading
>> the bearing with a crush sleeve instead of a spacer. No play! The reason
>> this has occured to me, is I am pretty sure one of those Part Numbers is a
>> pinion bearing in a GM differential...We sell little automatic lubricators
>> for things like sawmill machines, one could easily be adapted for this
>> purpose likely. Even a piece of narrow hose with a wick in it up to the
>> engine compartment might suffice..
>>
>> 0.0095 clearance IS a LOT. 0.002 is usual on similar bearings on rear
>> wheels. Typically 0.001"-0.006" is more usual.
>>
>> Last but not least, I seriously wonder how it could be possible to mail
>> order a pair of bearings with a spacer withing five/tenTHOUSANDTHS of an
>> inch precision. That just cant be right!
>>
>> Curiouser and curiouser. I'll get the smart guys to look at this for us,
>> they'll know!
>>
>> Brent Covey
>> Vancouver
>>
>>
>>
>>
>> > -Information on the inner race in order: Timken,.1209 (etched by
>> >hand),LM104949E,+,USA AL.
>>
>>
>> =====================================

>> >I'm reading a lot about bearings. Also, I'm hearing 0.0095" axial float
>for
>> >clearance. That's a lot. Since both or all components (hub, bearing,
>> >housing, etc.) are of similar metal composition they will expand ~the
>same;
>> >( 6.3 X 10^-6). The axial distance the cover is ~the same or close to the
>> >diameter of the bearing. All deltas can be multiplied by the linear
>> >expansion constant (temp & distance). One can also graphically depict or
>> >project the wobble at tire radius. 9.5 mils over 2 inches would become 95
>> >mils over 20 inches. This equates to ~3/32" and is very bad. Will lead to
>> >premature tire failure and cause wobble. At operating temp I would not
>> >recommend over 3 mils clearance (0.003 inch). Depending on the ABEC spec
>> >which determines internal clearance, I personally prefer 0.001".
>> >
>> >And, although temperature is also a predictive parameter, I prefer
>> >accelerometers and magnitude analysis. Vibration data through FFT
>analysis
>> >provides far greater exhaustive information with much greater accuracy in
>> >diagnosis. Has anyone considered the piezoelectric accelerometer or eddy
>> >current probe for their diagnostic panel? Just a thought. Acquiring data
>is
>> >one thing; diagnosis is another. Depending on who the analyst is one may
>be
>> >better off with idiot lights! Generally speaking, the motor home is a
>> >preventive maintenance item rather than a predictive maintenance item.
>It's
>> >kinda like the lubrication thing: $10/qt oil sees the same ring blow by
>as
>> >the $1.50 oil. The $10/qt oil may not suffer the same degradation but
>will
>> >see the same contamination. Solution, change oil often - say, 2kmi.
>> >
>> >I'm a consulting engineer specializing in bearing analysis, alignment and
>> >balancing. Lubrication plays a hand in all these. And, there is no
>> >substitute for good lubrication.
>> >I have but one request after being on this thread for two years. These
>past
>> >two years have resulted in doubling of the mail. Real issues are good,
>but,
>> >please directly E-mail specifics to a specific person to their personal
>> >E-mail address. Amen. I've been guilty from time to time. But, this isn't
>a
>> >posting board for personal messages. This might keep some of us from
>> >subscribing and unsubscribing all the time. Just food for thought, not
>> >wanting to stir up a stink or to add to the long list of E-mail. I like
>> >this thread and have profited from it. I think many may feel as I. Your
>not
>> >responding is appreciated. Thank you.
>> >
>> >With best regards; I'm
>> >Sincerely,
>> >Sam Pickens
>> >picksam
>> >
>> >
>> >
>>
>
>
>
>
 
Thanks for your thoughts, Will keep an eye and ear on look out, But
hopefully all will just keep rolling on!!! Will post if all just falls out.
Have a good and safe one!!

Ron&Gina
73 Pumpkin-Rose
Ft.Mohave,AZ.

- ----- Original Message -----
From:
To:
Sent: Monday, September 06, 1999 11:35 PM
Subject: Re: GMC: GMC front wheel bearings

> In my opinion the wallace hub weakens the knuckle since it has to be
> machined for the third bearing.
>
>

> >Tom, Who cares about controversy its all just an opinion. And hopefully
> >facts will align and all will track true. But why is the Wallace hub a
> >WEAKENED suspension? I have the Wallace hubs on my Pumpkin-Rose installed
by
> >P.O. 8-89 with 18,000 miles on them, Which seems to be doing just fine,
did
> >repack before last trip(JT-6), even tho I had 7k left before repack per
> >P.O., I do travel the highway and byways at higher then normal RV speeds
so
> >says the boss and would just like to get info if hubs are weakened? what
> >should I look for? Just so if need be I can start saving $ to replace
hubs.
> >But so far with my limited (3000mi.) GMC time all seem to be ok in the
> >Wallace bearing/hub set Oh yea and rock guard. A wondering mind what's to
> >know just to keep travel safe and problems down!!
> >
> >Ron&Gina
> >73 Pumpkin-Rose
> >Ft.Mohave,AZ.
> >
> >----- Original Message -----
> >From:
> >To:
> >Sent: Monday, September 06, 1999 6:09 PM
> >Subject: Re: GMC: GMC front wheel bearings
> >
> >
> >> I really do not want to start another controversey but here goes
anyway.
> >>
> >> Sam I would like to answer both your message and an earlier one by
Brent
> >> since they are of similar content.
> >> Both contain information that I disagree with.
> >>
> >> As a professonal engineer, and former Metrologist, I have a tendency to
> >over
> >> engineer everything I do. But in the case of the GMC front wheel
bearings
> >I
> >> am satisfied that there are no problems if they are serviced with the
> >> correct bearings, greased correctly, and assembled in within tolerance
> >hubs
> >> and knuckles, and lastly pressed on the hub in the correct manner. Past
> >> attempts at redesigning the hubs and kuckles such as the wallace hub,
in
> >my
> >> opinion resulted in expensive parts and a WEAKENED suspension.
> >>
> >> I have to say up front however that I have a pet peeve and that is
seeing
> >> engineering data that is masquerading as pertaining to the GMC
motorhome
> >> when in fact it does not. Sam both your comments and Brents for the
most
> >> part are not relevent to the GMC front wheel bearings and their failure
or
> >> fitting. The bearings, hubs, and knuckles are trouble free.
> >>
> >> In the case of brents remarks about the front wheel bearings he is
> >> incorrect,they are in fact a special bearing(hand etched with the axial
> >> clearance) even though they may appear to have the very same part
numbers
> >as
> >> a off the shelf Timken bearing. The correct GM front wheel bearing set
is
> >> fitted with a spacer (no two are alike in my experience) such that the
> >axial
> >> clearance is held to .0095". Why that clearance? Because General Motors
> >> Service Parts Operations Engineers (GMSPOE) did extensive tests and
> >analysis
> >> of the many failures of early GMC motorhomes in 1989-90 and concluded
that
> >> in a worse case scenario of a (small inside bearing diameter and
largest
> >> tolerance hub(2.0020")) that the assembled axial clearance was reduced
by
> >as
> >> much as .007". They therefore had Timken design a new front wheel
bearng
> >> set that had .0095" of axial clearance and 20% more load bearing
capacity.
> >> And yes it is possible to have a similarly looking roller bearing with
> >this
> >> increased load bearing capacity. How? Tighter tolerances, maybe diffent
> >cone
> >> angles and thus longer rollers. I really have not compared the
standard
> >> bearing with the new ones to see how they did it.
> >>
> >>
> >> Lets get to the bottom line on all of this since that is what most
netters
> >> want. We have beat this front wheel bearing problem to death and
concluded
> >> long ago that there was nothing wrong with the GM system. Install the
> >> correct bearings, pack them correctly, use in tolerance hubs and
knuckles,
> >> and you will have a trouble free hub. Don't do it and you are going to
> >have
> >> trouble. The choice as Arch says is yours. Want to break down on the
road
> >> far from home with a bad bearing? Than follow some of the alternative
> >advice
> >> I have seen in the last couple of days.
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> =========
> >> Skip
> >>
> >> Thats EXACTLY the info I needed.
> >>
> >> This is by no means a special bearing. There are still a couple
puzzling
> >> questions, not least of which is why they would fail at low mileages!
> >> Something is horribly amiss here- that bearing isnt working very hard
at
> >all
> >> in a GMC. Its considerably understressed. I have some theories I'll
bounce
> >> off engineering.
> >>
> >> Perhaps the press fit is too tight- the bearing and knuckle have a
similar
> >> coefficient of expansion, hence the interference fit should stay pretty
> >> constant. However, material yeilds mean that the bearings cant possibly
be
> >> fitted at any greater interference fit than about 0.004" maximum. You
> >> certainly could try, but in no time the materials would ease back to
> >around
> >> that anyhow. If they are installed much too tight in the beginning, and
> >then
> >> materials move and expand, there go the clearances!
> >>
> >> Maybe EP 80-90 would be a better lube for these, it would permit
> >preloading
> >> the bearing with a crush sleeve instead of a spacer. No play! The
reason
> >> this has occured to me, is I am pretty sure one of those Part Numbers
is a
> >> pinion bearing in a GM differential...We sell little automatic
lubricators
> >> for things like sawmill machines, one could easily be adapted for this
> >> purpose likely. Even a piece of narrow hose with a wick in it up to the
> >> engine compartment might suffice..
> >>
> >> 0.0095 clearance IS a LOT. 0.002 is usual on similar bearings on rear
> >> wheels. Typically 0.001"-0.006" is more usual.
> >>
> >> Last but not least, I seriously wonder how it could be possible to mail
> >> order a pair of bearings with a spacer withing five/tenTHOUSANDTHS of
an
> >> inch precision. That just cant be right!
> >>
> >> Curiouser and curiouser. I'll get the smart guys to look at this for
us,
> >> they'll know!
> >>
> >> Brent Covey
> >> Vancouver
> >>
> >>
> >>
> >>
> >> > -Information on the inner race in order: Timken,.1209 (etched
by
> >> >hand),LM104949E,+,USA AL.
> >>
> >>
> >> =====================================

> >> >I'm reading a lot about bearings. Also, I'm hearing 0.0095" axial
float
> >for
> >> >clearance. That's a lot. Since both or all components (hub, bearing,
> >> >housing, etc.) are of similar metal composition they will expand ~the
> >same;
> >> >( 6.3 X 10^-6). The axial distance the cover is ~the same or close to
the
> >> >diameter of the bearing. All deltas can be multiplied by the linear
> >> >expansion constant (temp & distance). One can also graphically depict
or
> >> >project the wobble at tire radius. 9.5 mils over 2 inches would become
95
> >> >mils over 20 inches. This equates to ~3/32" and is very bad. Will lead
to
> >> >premature tire failure and cause wobble. At operating temp I would not
> >> >recommend over 3 mils clearance (0.003 inch). Depending on the ABEC
spec
> >> >which determines internal clearance, I personally prefer 0.001".
> >> >
> >> >And, although temperature is also a predictive parameter, I prefer
> >> >accelerometers and magnitude analysis. Vibration data through FFT
> >analysis
> >> >provides far greater exhaustive information with much greater accuracy
in
> >> >diagnosis. Has anyone considered the piezoelectric accelerometer or
eddy
> >> >current probe for their diagnostic panel? Just a thought. Acquiring
data
> >is
> >> >one thing; diagnosis is another. Depending on who the analyst is one
may
> >be
> >> >better off with idiot lights! Generally speaking, the motor home is a
> >> >preventive maintenance item rather than a predictive maintenance item.
> >It's
> >> >kinda like the lubrication thing: $10/qt oil sees the same ring blow
by
> >as
> >> >the $1.50 oil. The $10/qt oil may not suffer the same degradation but
> >will
> >> >see the same contamination. Solution, change oil often - say, 2kmi.
> >> >
> >> >I'm a consulting engineer specializing in bearing analysis, alignment
and
> >> >balancing. Lubrication plays a hand in all these. And, there is no
> >> >substitute for good lubrication.
> >> >I have but one request after being on this thread for two years. These
> >past
> >> >two years have resulted in doubling of the mail. Real issues are good,
> >but,
> >> >please directly E-mail specifics to a specific person to their
personal
> >> >E-mail address. Amen. I've been guilty from time to time. But, this
isn't
> >a
> >> >posting board for personal messages. This might keep some of us from
> >> >subscribing and unsubscribing all the time. Just food for thought, not
> >> >wanting to stir up a stink or to add to the long list of E-mail. I
like
> >> >this thread and have profited from it. I think many may feel as I.
Your
> >not
> >> >responding is appreciated. Thank you.
> >> >
> >> >With best regards; I'm
> >> >Sincerely,
> >> >Sam Pickens
> >> >picksam
> >> >
> >> >
> >> >
> >>
> >
> >
> >
> >
>
 
25,000 miles? 18,675,000 rotations. Replace bearings every year. In
industry at 3600 RPM, 24 hours a day, 365 days per year one would expect to
run at least 3 years or you have a poor installation. 5,184,000 revs per
day @3600, so you'd replace that bearing every week.

I have 32 years experience with over 20 on bearings and use real time
analyzers (FFT analysis) and piezoelectric accelerometers and have the
ability to pin point failure right down to the defective component (inner
or outer race, cage or ball, etc.). I have done R&D projects for the
automotive industry. Dear Sweet Lord; give me grace.

It's beyond my comprehension that anyone would consider replacing bearings
every 25,000 miles. That's the worst advise I've ever heard. One should
loose one's credibility making such statements. The horse is dead. On to KY
men.

With best regards; I'm
Sincerely,
Sam Pickens
picksam
 
Arch and all,

Approaching one's vehicle. Familiarity breeds exempt. Exemption comes by
knowing. How well do we know our vehicle? Have you recently purchased and
assuming everything is OK? At the first Spring or Fall whichever comes
first, pull the wheel, inspect the brakes and lubrication of the bearings,
etc. If I have suspicion of anything, I have a tendency to attach an
accelerometer and drive down the road gathering data for analysis before
visual inspection. And/or from said analyses I may determine to replace the
bearing even before visual inspection. On the other hand said analyses may
give me confidence to continue operation without visual inspection.

Sorry about the rambling. Yes, I do analyses of bearings while driving down
the road. I've also performed testing on vehicles while on a rack. I did a
Jaguar and determined the drive shaft was out of balance. They didn't
believe me as they told me that was the drive shaft they just had balanced.
They were fully confident the DS was OK. I soured the problem to the DS and
maintained the transmission and hogs head were OK. The problem was resolved
when the DS was again balanced. Setting DS's up for race is interesting but
that's another topic. I have full confidence on those data.

One bearing doesn't necessarily relate to the next. For example; the L side
can be OK while the R side is bad. Analysis can determine this. Now to the
trick. Can this transfer from one person to another? NO! But, I believe
basic guidelines could be established. A random starting point could be
established; say at five g's 0-P overall.

How to obtain that data. One approach is to instrument the vehicle with
onboard monitoring. Another, portable monitoring device that could even be
transported or swapped between GMCers. Breaking down on the highway can
cost five days unless you're stinking, filthy rich. I only need to get the
rich part right. One may instrument a vehicle for ~$1500 - I'm guessing
(six transducers, cabling, electrical supply {either -18, -24 or -27
volts}, and a digital readout). Once it has been determined that 5 g's is
the flag point that alerts to inspection/replacement or whatever value that
is finally determined, then one could run with peace of mind. Lubrication
can be a veribile, how much wet driving vs dry driving and do you drive
through creeks? The overall approach won't allow monitoring of lubrication
but FFT analyses will. Replace the digital readout with an FFT analyzer and
you're ready to run on Indy. Those data can also be transmitted via cell
phone. Anyone wanting to replace their dash with a computer -- monitor all
parameters. It isn't that difficult anymore. Where do you want to take this
thing? Money is the only limit, all else is easy. Very easy.

I hope this helps to provide insight. This is pumping me up to want to do
it. Good preventive maintenance should void or kill the project. But,
predictive maintenance is does have cost effective virtues too. It will
reduce maintenance while maximizing life. And, life is too short to drink
bad wine. Besides, a motor home is throw away money for most. Unless,
you're like me - single, travel all the time, play as much as I can. That's
right, I'm broke but enjoy bitching about it. I'm sitting in Big Jim now
writing this thread. I travel every season, even winter in MI and summer in
FL. I will venture to say, there isn't anyone out there that spends more
time in their MH that me. I have to depend on mine, it's a way of life. I
hope I haven't bored anyone with my ramblings. May the good Lord take a
liking to ya.

With best regards; I'm
Sincerely,
Sam Pickens
picksam
 
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