Inner CV Joint to Final Drive Flange Bolts

[robert mueller]

G'day,

I am working on putting the Blue Streak's front end back together and got t=
o
thinking about all the problems people have noted with the bolts that hold
the inner CV joint to the final drive flanges coming loose.

I decided to drill out my bolts and safety wire them, problem solved!

I checked McMaster Carr and found they sell Allen socket head 3/8 x 24 bolt=
s
that are drilled with holes for safety wire. The safety wire holes are
0.0625 in diameter. The part number is:

90117A255: 1 1/4 inch long (measured under the head) @ $8.75 for a pack of
10 Note: these are long enough to install the lock washers.

If you check the specs on these bolts you will see that they have a tensile
strength of 180,000 psi, this meets / exceeds grade 8.

The McMaster Carr part number for 0.032 diameter 302/304 stainless steel
safety wire is 8860K63 @ $13.50 for a one pound can.

There are six bolts on each flange so you will have to order two packs.

If you want you can buy a pair of safety wire pliers from Harbor Freight;
see item 45340-7VGA for a pair 8 1/4 inches long for $6.99 or item
45341-3VGA for a pair 10-1/2 inches long for $7.99. =20

Finally when you safety wire the bolts make sure you run the wire through
the holes so that it pulls the bolts in the tighten (clockwise) direction!

http://www.whizwheels.com/Tips/safetywiring.html

Regards,
Rob Mueller
Sydney, Australia
75 - Avion - AUS - The Blue Streak
75 - Avion - USA - Double Trouble

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[Gene Fisher]

looks like a great idea. so

since you are done, you are not going to use these?
how are your going to calculate the torque ?
wonder how we are going to get them out if they strip the allen?

I like it, will post it on my site as an option. I know many folks
have used allen bolts here for years. Always makes me wonder, my
coach has gone 30 years and never lost a bolt in the last 10 years.
If they cannot tighten a regular bolt, wonder if they can wire an
allen bolt? Guess we will see.

McMaster is our friend ;>)

thanks
gene

> G'day,
>
> I am working on putting the Blue Streak's front end back together and got to
> thinking about all the problems people have noted with the bolts that hold
> the inner CV joint to the final drive flanges coming loose.
>
> I decided to drill out my bolts and safety wire them, problem solved!
>
> I checked McMaster Carr and found they sell Allen socket head 3/8 x 24 bolts
> that are drilled with holes for safety wire. The safety wire holes are
> 0.0625 in diameter. The part number is:
>
> 90117A255: 1 1/4 inch long (measured under the head) @ $8.75 for a pack of
> 10 Note: these are long enough to install the lock washers.
>
> If you check the specs on these bolts you will see that they have a tensile
> strength of 180,000 psi, this meets / exceeds grade 8.
>
> The McMaster Carr part number for 0.032 diameter 302/304 stainless steel
> safety wire is 8860K63 @ $13.50 for a one pound can.
>
> There are six bolts on each flange so you will have to order two packs.
>
> If you want you can buy a pair of safety wire pliers from Harbor Freight;
> see item 45340-7VGA for a pair 8 1/4 inches long for $6.99 or item
> 45341-3VGA for a pair 10-1/2 inches long for $7.99.
>
> Finally when you safety wire the bolts make sure you run the wire through
> the holes so that it pulls the bolts in the tighten (clockwise) direction!
>
> http://www.whizwheels.com/Tips/safetywiring.html
>
> Regards,
> Rob Mueller
> Sydney, Australia
> 75 - Avion - AUS - The Blue Streak
> 75 - Avion - USA - Double Trouble
>
> To unsubscribe or change your settings - http://www.gmcnet.org/settings.htm
> Donate to support GMCnet - http://www.gmcnet.org/support.html
>

--
Gene Fisher -- 77PB/ore/ca
"Give a man a fish; you have fed him for today --- give him a URL and -------
http://gmcmotorhomeinfo.com/
Alternator Protection Cable
http://gmcmotorhomeinfo.com/APC.html

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[ulmer james d - denver co]

Comments:

By the time you get to that large of Allen head bolt, stripping out the
hex is rarely a problem.

I'd use the standard torque tables for a grade 8 bolt.

I hate lock washers. Their only real function is to keep an already
loose bolt or nut from falling off. In this kind of application, I like
grade 8/hardened/carburized SAE flat washers. They provide a smooth,
consistent surface for the bolt head. That means the torque applied
actually goes toward tensioning the bolt and not grinding on a grain of
sand or burr on the flange.

If the flanges are in good condition and the bolts properly installed,
you should never have any problems. That is just a might big IF with
30-year-old equipment. When I picked up my SOB Cortez, I was able to
look down through the hatch and see daylight between the final drive and
the flange. That is a disconcerting experience, to say the least. It has
been happy with Allen head bolts ever since. Hint - They are commonly
available in limited quantities at ACE hardware stores. That can be a
lifesaver on weekends.

Safety wire is kind of a pain in the rear but it sure does keep
airplanes from falling out of the sky. That's pretty good evidence that
it really works.
=20
Big Jim

-----Original Message-----
From: Mr.erf ERFisher [mailto:mr.erfisher]=20
Sent: Tuesday, May 20, 2008 6:15 AM
To: gmclist
Subject: Re: [gmclist] Inner CV Joint to Final Drive Flange Bolts

looks like a great idea. so

since you are done, you are not going to use these?
how are your going to calculate the torque ?
wonder how we are going to get them out if they strip the allen?

I like it, will post it on my site as an option. I know many folks
have used allen bolts here for years. Always makes me wonder, my
coach has gone 30 years and never lost a bolt in the last 10 years.
If they cannot tighten a regular bolt, wonder if they can wire an
allen bolt? Guess we will see.

McMaster is our friend ;>)

thanks
gene

> G'day,
>
> I am working on putting the Blue Streak's front end back together and
got to
> thinking about all the problems people have noted with the bolts that
hold
> the inner CV joint to the final drive flanges coming loose.
>
> I decided to drill out my bolts and safety wire them, problem solved!
>
> I checked McMaster Carr and found they sell Allen socket head 3/8 x 24
bolts
> that are drilled with holes for safety wire. The safety wire holes are
> 0.0625 in diameter. The part number is:
>
> 90117A255: 1 1/4 inch long (measured under the head) @ $8.75 for a
pack of
> 10 Note: these are long enough to install the lock washers.
>
> If you check the specs on these bolts you will see that they have a
tensile
> strength of 180,000 psi, this meets / exceeds grade 8.
>
> The McMaster Carr part number for 0.032 diameter 302/304 stainless
steel
> safety wire is 8860K63 @ $13.50 for a one pound can.
>
> There are six bolts on each flange so you will have to order two
packs.
>
> If you want you can buy a pair of safety wire pliers from Harbor
Freight;
> see item 45340-7VGA for a pair 8 1/4 inches long for $6.99 or item
> 45341-3VGA for a pair 10-1/2 inches long for $7.99.
>
> Finally when you safety wire the bolts make sure you run the wire
through
> the holes so that it pulls the bolts in the tighten (clockwise)
direction!
>
> http://www.whizwheels.com/Tips/safetywiring.html
>
> Regards,
> Rob Mueller
> Sydney, Australia
> 75 - Avion - AUS - The Blue Streak
> 75 - Avion - USA - Double Trouble
>
> To unsubscribe or change your settings -
http://www.gmcnet.org/settings.htm
> Donate to support GMCnet - http://www.gmcnet.org/support.html
>

--=20
Gene Fisher -- 77PB/ore/ca
"Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhomeinfo.com/
Alternator Protection Cable
http://gmcmotorhomeinfo.com/APC.html

To unsubscribe or change your settings -
http://www.gmcnet.org/settings.htm
Donate to support GMCnet - http://www.gmcnet.org/support.html

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[ulmer james d - denver co]

I was just browsing McMaster-Carr and, if you have concerns about an
Allen head bolt, take a look at item 91271A644. It is similar to an
Allen head but with a 12-point external head. Use a 12-point socket and
apply all the torque you want. Same overall outside diameter as the
Allen heads ones.

Big Jim

-----Original Message-----
From: Ulmer, James D - Denver, CO [mailto:james.d.ulmer]=20
Sent: Tuesday, May 20, 2008 6:49 AM
To: gmclist
Subject: RE: [gmclist] Inner CV Joint to Final Drive Flange Bolts

Comments:

By the time you get to that large of Allen head bolt, stripping out the
hex is rarely a problem.

I'd use the standard torque tables for a grade 8 bolt.

I hate lock washers. Their only real function is to keep an already
loose bolt or nut from falling off. In this kind of application, I like
grade 8/hardened/carburized SAE flat washers. They provide a smooth,
consistent surface for the bolt head. That means the torque applied
actually goes toward tensioning the bolt and not grinding on a grain of
sand or burr on the flange.

If the flanges are in good condition and the bolts properly installed,
you should never have any problems. That is just a might big IF with
30-year-old equipment. When I picked up my SOB Cortez, I was able to
look down through the hatch and see daylight between the final drive and
the flange. That is a disconcerting experience, to say the least. It has
been happy with Allen head bolts ever since. Hint - They are commonly
available in limited quantities at ACE hardware stores. That can be a
lifesaver on weekends.

Safety wire is kind of a pain in the rear but it sure does keep
airplanes from falling out of the sky. That's pretty good evidence that
it really works.
=20
Big Jim

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[robert mueller]

Gene,

COMMENTS IN CAPS BELOW.

Regards
Rob Mueller
Sydney, Australia
75 - Avion - AUS - The Blue Streak
75 - Avion - USA - Double Trouble

-----Original Message-----
From: Mr.erf ERFisher [mailto:mr.erfisher]
Sent: Tuesday, 20 May 2008 10:15 PM
To: gmclist
Subject: Re: [gmclist] Inner CV Joint to Final Drive Flange Bolts

looks like a great idea.
THANKS.

so since you are done, you are not going to use these?
I HAVEN'T COMPLETED THE JOB YET, HOWEVER, THE BLUE STREAK ALREADY HAD ALLEN
BOLTS ALL I DID WAS DRILL THE SAFETY WIRE HOLES.

how are your going to calculate the torque?
I HAVE A SET OF ALLEN SOCKET WRENCHES THAT ATTACH TO MY 1/2 DRIVE TORQUE
WRENCH.

wonder how we are going to get them out if they strip the allen?
THE SOCKETS IN THESE BOLTS ARE 5/16 INCH AND ARE HARD TO STRIP. IF YOU DID
STRIP ONE IT WOULD BE RELATIVELY EASY TO DRILL IT OUT AS THE SOCKET HEAD
GUIDES THE DRILL.

I like it, will post it on my site as an option.
GOOD IDEA. WAIT UNTIL I FINISH THE JOB I'LL PROVIDE MORE DETAILS AND WRITE
SOME DETAILED INSTRUCTIONS FOR THE MECHANICALLY DECLINED! ;-)

I know many folks have used allen bolts here for years. Always makes me
wonder, my coach has gone 30 years and never lost a bolt in the last 10
years. SOMETHING CALLED PREVENTATIVE MAINTENANCE MAYBE? ;-)

If they cannot tighten a regular bolt, wonder if they can wire an
allen bolt? Guess we will see.
THAT'S WHY I INCLUDED THE LINK TO THE SAFTEY WIRE INSTUCTIONS.

McMaster is our friend ;>)
UNFORTUNATELY SUBSEQUENT TO 9-11 THEY STOPPED SHIPPING OVERSEAS UNLESS YOU
HAD AN ACCOUNT WITH THEM BEFORE 9-11. WHEN I NEED STUFF FROM THEM I ASK
FRIENDS TO GET THE ITEM FOR ME AND SEND IT. JIM K GOT ME A SET OF CLUTCH
DRIVE BITS AND INCLUDED THEM IN A PARTS ORDER I GOT FROM HIM.

thanks
gene
.org/support.html

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[robert mueller]

Jim,

COMMENTS BELOW IN CAPS.

Regards,
Rob Mueller
Sydney, Australia
75 - Avion - AUS - The Blue Streak
75 - Avion - USA - Double Trouble

-----Original Message-----
From: Ulmer, James D - Denver, CO [mailto:james.d.ulmer]=20
Sent: Wednesday, 21 May 2008 12:07 AM
To: gmclist
Subject: RE: [gmclist] Inner CV Joint to Final Drive Flange Bolts

I was just browsing McMaster-Carr and, if you have concerns about an
Allen head bolt, take a look at item 91271A644. It is similar to an
Allen head but with a 12-point external head. Use a 12-point socket and
apply all the torque you want. Same overall outside diameter as the
Allen heads ones.
UNFORTUANTELY THESE BOLTS DON'T HAVE SAFETY WIRE HOLES IN THEM. I ALSO NOTE=
D
THAT THEIR TENSILE STRENGTH IS GIVEN AS 170,000 PSI WHEREAS THE ALLEN BOLTS
DRILLED FOR SAFETY WIRE IS 180,000 PSI.

By the time you get to that large of Allen head bolt, stripping out the
hex is rarely a problem.
AGREED! THE SOCKET IS 5/16 IN.

I'd use the standard torque tables for a grade 8 bolt.
THE MAINTENANCE MANUAL X-7525 TORQUE SPECIFICATION TABLE ON PAGE 3A-22
SPECIFIES THE TORQUE TO BE 75 FT LB. I'LL REPORT BACK IF I HAVE ANY PROBLEM=
S
TORQUING THEM TO THIS LEVEL.

I hate lock washers. Their only real function is to keep an already
loose bolt or nut from falling off. In this kind of application, I like
grade 8/hardened/carburized SAE flat washers. They provide a smooth,
consistent surface for the bolt head. That means the torque applied
actually goes toward tensioning the bolt and not grinding on a grain of
sand or burr on the flange.
I WAS GOING TO RE-USED THE LOCK WASHERS BECAUSE I HAD THEM, I'M GOING TO GE=
T
SOME GRADE 8 HARDENED WASHERS AS YOU SUGGESTED.

If the flanges are in good condition and the bolts properly installed,
you should never have any problems. That is just a might big IF with
30-year-old equipment. When I picked up my SOB Cortez, I was able to
look down through the hatch and see daylight between the final drive and
the flange. That is a disconcerting experience, to say the least. It has
been happy with Allen head bolts ever since. Hint - They are commonly
available in limited quantities at ACE hardware stores. That can be a
lifesaver on weekends.
AGREED! I FIGURED I'D ADD THE SAFETY WIRE TO REDUCE THE CHANCES OF THE BOLT=
S
COMING OUT TO SLIM TO NONE!

Safety wire is kind of a pain in the rear but it sure does keep airplanes
from falling out of the sky. That's pretty good evidence that it really
works.
I'D SAY IT WAS MORE OF A PAIN IN THE FINGERS; I WAS CONSTANTLY STABBING
MYSELF WITH THE ENDS OF THE WIRE WHEN I A MECHANICAL ACCESSORIES REPAIRMAN
IN THE USAF!
=20
Big Jim

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[ulmer james d - denver co]

OK, I have a hard time with this one. The OEM bolts were special and
were not supposed to be reused. Indication is they may be 'torque to
yield' fasteners. The spec for them is 75 ft lbs. Standard grade 8
charts say about 45 for a 3/8 bolt. If I went to 75 with any
replacement, I'd consider it non-reusable. Even grade 8+ bolts will
likely show some permanent deformation if torqued that high.

Dang! Why is nothing ever simple?

Big Jim

=20

-----Original Message-----
From: Rob Mueller [mailto:robmueller]=20
Sent: Tuesday, May 20, 2008 9:13 AM
To: gmclist
Subject: RE: [gmclist] Inner CV Joint to Final Drive Flange Bolts

Jim,

COMMENTS BELOW IN CAPS.

Regards,
Rob Mueller
Sydney, Australia
75 - Avion - AUS - The Blue Streak
75 - Avion - USA - Double Trouble

...

I'd use the standard torque tables for a grade 8 bolt.
THE MAINTENANCE MANUAL X-7525 TORQUE SPECIFICATION TABLE ON PAGE 3A-22
SPECIFIES THE TORQUE TO BE 75 FT LB. I'LL REPORT BACK IF I HAVE ANY
PROBLEMS
TORQUING THEM TO THIS LEVEL.

Big Jim

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[dan gregg]

I have had some come loose. I was at Bert and Fay's when one of our fellow GMCer's was stranded with his falling completely out. I had Bert order me a new set from Mc/C. We plan to drill them and put in when I get back to the coach in June. I tend to learn from bad experiences, both mine and others. I think dirlling and safety wire is the best way to stop this.
Dan
--
Dan & Teri Gregg

http://www.danandteri.blogspot.com

Halon Automatic Fire Extinguishers

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[chuck garton]

In my thirty years of GMC owership, I only had one instance of these
bolts loosening. This was due to the right wheel bearing failing. All
6 bolts would be loose after a 500 mile run. I tried locktite etc.
Safety wire was out because I didn't have a drill bit that would work
on the 12 point bolts. I later found out these were grade 14 bolts.

Chuck Garton
455 Kingsley
Ridgecrest, CA

>
>
> I have had some come loose. I was at Bert and Fay's when one of our fellow GMCer's was stranded with his falling completely out. I had Bert order me a new set from Mc/C. We plan to drill them and put in when I get back to the coach in June. I tend to learn from bad experiences, both mine and others. I think dirlling and safety wire is the best way to stop this.
> Dan
> --
> Dan & Teri Gregg
>
> http://www.danandteri.blogspot.com
>
> Halon Automatic Fire Extinguishers
>
> To unsubscribe or change your settings - http://www.gmcnet.org/settings.htm
> Donate to support GMCnet - http://www.gmcnet.org/support.html
>

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[robert mueller]

Jim,

Agreed!=20

I did not do a good job on my homework! I assumed that the 3/8" x 24 Allen
head bolts were the correct bolts!

This morning I checked the parts manual and noted that the original bolts
are a shouldered hex head bolt (ref. pg. 1-8 item 21 p/n 394777 BOLT -
washer head (.432 I.D. X .530 O.D.). I'm going to measure the holes in the
inner CV joint flange that these bolts go through; I'll bet dollars to
donuts that it is a smidgen bigger than .432! By the way I noted that the
quantity is wrong in the manual as it specifies 5!

I then went to the Maintenance Manual and noted:

"4. Move R.H. drive axle assembly toward front of vehicle and align with
R.H. output shaft. Install NEW attaching bolts and torque to 75 ft. lb."

The word NEW is capitalized in the manual which indicates you were correct
when you noted they were a one time use bolt.

Being an anally retentive perfectionist I am in a quandary as to what to do
about this! I searched the internet for the past hour trying to find a bolt
like the ones GMC specified, no luck! I have decided on a two front attack
on the problem!

1) a. Buy 12 new grade 8 Allen bolts
b. Buy 12 new case hardened washers
c. Drill them for safety wire holes
d. Install the Allen head bolts and torque them to 45 ft. lb.
e. Safety wire the bolts

2) Does anyone know where we can buy the OEM bolts?

I did some thinking and it might be possible that the people that have had
problems with these bolts because they re-used the original bolts or torque=
d
grade 8 bolts (hex or Allen head) to the 75 ft lb as noted in the manual. I
would think this would stretch the bolts and possibly cause them to fatigue=
,
loose torque, and come loose?

Regards,
Rob Mueller
Sydney, Australia
75 - Avion - AUS - The Blue Streak
75 - Avion - USA - Double Trouble

-----Original Message-----
From: Ulmer, James D - Denver, CO [mailto:james.d.ulmer]=20
Sent: Wednesday, 21 May 2008 1:58 AM
To: gmclist
Subject: RE: [gmclist] Inner CV Joint to Final Drive Flange Bolts

OK, I have a hard time with this one. The OEM bolts were special and
were not supposed to be reused. Indication is they may be 'torque to
yield' fasteners. The spec for them is 75 ft lbs. Standard grade 8
charts say about 45 for a 3/8 bolt. If I went to 75 with any
replacement, I'd consider it non-reusable. Even grade 8+ bolts will
likely show some permanent deformation if torqued that high.

Dang! Why is nothing ever simple?

Big Jim

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[ken & dennis 2013]

GMC Lesson #1: Always check Mr. ERF's site first:

http://users.california.com/~eagle/front.html

The bolts and washers Rick suggests there are what I've used for at
least 7-8 years and over 50,000 miles. Never had a loose one, broken
one, or stripped one. That's good 'nuff for me. The fact that they're
fully threaded rather than shouldered bothered me for about 15 seconds
-- long enough to realize that friction between the flat plates bears
the torque, NOT shear loading of the bolts. My success with blue
Locktite precludes me fooling with safety wire.

Oh yeah, over that period, I've had each axle loose several times --
occasionally I might replace the bolts, but not always. No, I don't
take 'em apart just for fun nor to be sure they're still clean.

Ken H.

> Jim,
>
> Agreed!...

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[robert mueller]

G'day,

After sending my last message on these bolts I worked my way further down
the list of messages in my in-basket to discover an off net reply from a GM=
C
netter (who wished to remain anonymous) advising:

Quote:

The OEM flange bolts are available from Cinnabar for $2 each, not a high
price for the proper item. They are still available (but more expensive) at
GM dealers under part number 394777. Cadillac dealers might have them in
stock for FWD Eldorado. They can also be drilled for wire locking. An 11 mm
socket with 12 points works well on the OEM flange bolts, a better fit than
a 7/16" socket.
=20
BTW, I see in your later post that you mention lock washers, the GM part
number for the high-collar lock washer for this application is 9439512, als=
o
available from Cinnabar.

Unquote:

For the hell of it I called the local Holden dealer and gave him the part
numbers, no luck!

Because I am an anally retentive perfectionist I'll just buy the proper
bolts and washers from Cinnabar and drill them out for safety wire using
cobalt drills! ;-)

Thanks to everybody that commented!

As Gilda Radner used to say on Saturday Night Live "Oh, Never mind!"

Rob Mueller
Sydney, Australia
75 - Avion - AUS - The Blue Streak
75 - Avion - USA - Double Trouble

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[gordon & the "tin gerbil"]

Rob;
My first thought is that the bolts holding the flex plate to the crank
and the torque converter to the flex plate on GM's since 1955 were
labeled as "one time use".
I can't count the number of vehicles or number of times I have re-used
these bolts without failure. If I was concerned with the axle assembly
bolts, my thought would be to first run a new nut down the threads by
hand which would show if they are stretched. I realize this will not
show they if they will stretch when torqued to 75 lbs. The other
thought is take a used bolt, clamp it in a vise and break it off with a
torque wrench. Cave man testing at it's finest.
Gordon

> Jim,
>
> Agreed!
>
> The word NEW is capitalized in the manual which indicates you were correct
> when you noted they were a one time use bolt.
>
> Being an anally retentive perfectionist I am in a quandary as to what to do
> about this! I searched the internet for the past hour trying to find a bolt
> like the ones GMC specified, no luck! I have decided on a two front attack
> on the problem!
>
> 1) a. Buy 12 new grade 8 Allen bolts
> b. Buy 12 new case hardened washers
> c. Drill them for safety wire holes
> d. Install the Allen head bolts and torque them to 45 ft. lb.
> e. Safety wire the bolts
>
> 2) Does anyone know where we can buy the OEM bolts?
>
> I did some thinking and it might be possible that the people that have had
> problems with these bolts because they re-used the original bolts or torqued
> grade 8 bolts (hex or Allen head) to the 75 ft lb as noted in the manual. I
> would think this would stretch the bolts and possibly cause them to fatigue,
>
>

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[matt & mary colie]

Rob,

About bolting drive flanges.

Someone suggested that these may be single use because they are torque to yield fasteners.
This is highly unlikely.
Torque to yield fasteners simply cannot be tensioned by installing to a final torque. If one examines the torque/angle data for a torque to yield installation, he will find that there is a plateau in the curve that might appear flat to the torque wrenches that even the best equipped shop would have available.

There are other more likely possibilities here. One is that the maintenance manual editors wrote this in to prevent warranty claims that would result from a repeated stress failure (unlikely, but some engineers are a little paranoid). The other is that grade 14 (MS20K) fasteners are not uncommon in aircraft. Aircraft (gee, you might just remember this) almost always scrap fasteners after the initial installation. This is largely because high strength alloy fasteners a very prone to galling and internal stress cracking. These fasteners are most commonly used with a prevailing torque locknut that will cause some deformation of the thread profile, so they are always scrapped in this case. (It is really unhandy when parts fall off in flight.)

As a past member of the ASTM Bolting Technology Committee member, would I reuse these fasteners?
You bet. (Actually, I just did when I replaced the outer CV boots.) If one of these fasteners was to fail on installation. It would most likely be a clean break that can be easily unthreaded from the drive flange. Be very certain that the threads of both the flange and the fastener are clean before you start.

Good Luck
--
Matt & Mary Colie
'73 Glacier 23 Chaumiere (say show-me-air)
SE Michigan

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[RJW]

Matt,

Could this be the same situation I recently ran into while replacing wheel
bearings on my old Ford Explorer?

Reference the wheel hub nut that holds the axle in place, the service manual
states "Remove the wheel hub nut and discard it. NEVER reuse the wheel hub
nut." I found that I could easily buy a bearing and hub assembly for my
truck, but when I wanted to buy the " wheel hub nut " all the parts places,
including the local Ford dealer said that "is a special order item". Why is
it a special order part when you are supposed to get a new one with each
bearing replacement? I special ordered one because I was afraid of the
warning to "not reuse the wheel hub nut". Apparently, most places,
including our Ford dealer reuse the hub nut when they replace bearings.

Richard Waters
1976 Palm Beach, still all green!
Troy, Michigan USA
Website: www.PalmBeachGMC.com

> -----Original Message-----
> Subject: Re: [gmclist] Inner CV Joint to Final Drive Flange Bolts
>
> About bolting drive flanges.
>
> Someone suggested that these may be single use because they are torque
> to yield fasteners. This is highly unlikely.
> There are other more likely possibilities here. One is that the
> maintenance manual editors wrote this in to prevent warranty claims that
> would result from a repeated stress failure (unlikely, but some
> engineers are a little paranoid).

> As a past member of the ASTM Bolting Technology Committee member, would
> I reuse these fasteners? You bet. (Actually, I just did when I replaced
> the outer CV boots.)
> If one of these fasteners was to fail on installation. It would most
> likely be a clean break that can be easily unthreaded from the drive
> flange. Be very certain that the threads of both the flange and the
> fastener are clean before you start.
>
> Good Luck
> --
> Matt & Mary Colie

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[Rdenney]

Rob Mueller writes...

> Being an anally retentive perfectionist I am in a quandary as to what to do
> about this! I searched the internet for the past hour trying to find a bolt
> like the ones GMC specified, no luck! I have decided on a two front attack
> on the problem!

> 1) a. Buy 12 new grade 8 Allen bolts
> b. Buy 12 new case hardened washers
> c. Drill them for safety wire holes
> d. Install the Allen head bolts and torque them to 45 ft. lb.
> e. Safety wire the bolts

Just buy these from McMaster-Carr:

91271A644 12-point flange head cap screw 3/8"-24 thread, 1=1/4"
length, fully threaded, $9.21 in packs of 25.

The minimum tensile strength is 170 ksi and it exceed Grade 8.

I can't imagine what drill bit I own that would drill a hole in 12 of
these for safety wire. And safety wire is just the same as lock
washers--its purpose is to prevent the bolt from falling out if it
gets loose. That should not happen if properly torqued to being with.
The reason these are torqued to yield is two-fold:

1. It results in very even clamping force around the six bolts, and

2. It stretches the bolt enough so that compression strain does not
ever cause it to go slack, which is what can allow it to loosen.

But the yielding means you cannot tighten them a second time.

> 2) Does anyone know where we can buy the OEM bolts?

They are still available from GM, but get your checkbook ready. I have
seen them priced at up to over $5 per bolt.

> I did some thinking and it might be possible that the people that have had
> problems with these bolts because they re-used the original bolts or torqued
> grade 8 bolts (hex or Allen head) to the 75 ft lb as noted in the manual. I
> would think this would stretch the bolts and possibly cause them to fatigue,
> loose torque, and come loose?

The cross-sectional area of a 3/8-24 bolt is .08782 square inches,
using the Industrial Fasteners Institute formula. The force exerted
across that area is F = T / KD, where T is the torque in inch-pounds,
K is a dimensionless factor that is in the range of .16 to .27 for
plain steel on steel, and D is the nominal diameter of the bolt. At 70
ft-lbs (840 inch-lbs), the the extremes of the K-factor range result
in stresses ranging from 95 ksi to 160 ksi. Grade 8 bolts have a
tensile strength of 150 ksi and a yield strength of 120 ksi. The ASTM
A574 bolts listed above have a minimum tensile strength of 170 ksi,
and exceed Grade 8, class 10.9, or other standard typically used by
the automotive industry. I would NOT use anti-sieze on these
bolts--that could lower the K factor to as little as .1, which could
allow the rated torque to exceed the strength of the bolt. You'll know
this happens, because the torque wrench will fall on your head with
the bolt head still in the socket.

I don't see reports of people breaking them, but I do see reports of
them coming loose, but not for people who tighten them to spec. I
suspect proper tightening is the real solution to the problem of
coming loose.

Rick "thinking Grade 8 isn't good enough when tightened to spec"
Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

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[Rdenney]

Matt Colie writes...

> Torque to yield fasteners simply cannot be tensioned by installing
> to a final torque. If one examines the torque/angle data for a
> torque to yield installation, he will find that there is a plateau
> in the curve that might appear flat to the torque wrenches that even
> the best equipped shop would have available.

I had forgotten this and Matt is absolutely right.

But we should remember that bolts are not machined from homogeneous
material. They are stamped in a forge. Thus, the yield strength of the
material varies across the section. So, when tightened to values close
to the yield strength, you can still expect micro-yielding in parts of
the cross-section that have high residual stresses.

But this is a good thing, because it serves to relieve bolt stresses
resulting from the method of manufacture. By forcing internal bits of
the bolt that might have residual stresses to yield, those residual
stresses are relieved and the bolt becomes more evenly stressed and
more resistant to fatigue cracking.

We learned this with bicycle spokes. Standard wheel-building technique
for bicycle wheels involves tightening them to a high percentage of
yield strength and then temporarily overstressing them. We do that by
squeezing parallel pairs of spokes together hard after tensioning the
spokes, which increases their stress considerably over the stress
resulting from initial tensioning. This allows the bits of the spoke
cross-section that have high residual stresses to yield, which results
in more even stress across the spoke. Spoke ends are stamped, just
like bolts. Spokes that have not been stress-relieved in this fashion
tend to break from fatigue. (Bicycle wheel spokes are subject to
maximum load just sitting there. Loads on bicycle wheels serve to
unload the spokes only because of compression deflection of the rim.
That's why they have to be tight--so that unloading them under load
never allows them to go slack, which is what allows the spoke nipple
to turn and the wheel to go out of true.)

And that reminds me that used spokes are not only reused, but they are
prized, because their stresses have been proven to be relieved by
having not failed from fatigue. So, maybe it's okay to reuse those
bolts. But when you buy them from McMaster, they are not expensive so
it does no harm.

Rick "second-guessing what was in the mind of the design engineer"
Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

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[steve southworth]

OK - after all this talk on the bolts and possible replacements, is the consensus to use the lock-washer or replace it with a high grade flat washer, or just forget it all together as the bolt is washer head? This question brought to you by an electric guy who does his own mechanical work.
--
Steve Southworth
1974 Glacier TZE064V100150
Palmyra WI

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[Rdenney]

Steve Southworth writes...

> OK - after all this talk on the bolts and possible replacements, is
> the consensus to use the lock-washer or replace it with a high grade
> flat washer, or just forget it all together as the bolt is washer
> head? This question brought to you by an electric guy who does his own mechanical work.

The factory used the lock washers, and I would, too. I can't think of
any reason not to.

Rick "noting that the 'high-collar' lock washers are like the
originals" Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

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[robert mueller]

Rick,

Thanks for you comments.

1) The Allen headed bolts from McMaster Carr are rated at 180,000 psi which
also exceeds grade 8.

Allen Head Bolt
Part Number: 90117A255
Minimum Tensile Strength 180,000 psi

Flange Head Bolt
Part Number: 91271A644
Minimum Tensile Strength 170,000 psi

2) I only drilled safety wire holes in one Allen bolt using a cobalt drill
bit. It wasn't a problem.

3) I've sent an email to Cinnabar requesting a price for the OEM bolt and
washer; I'll post the info when received.

4) I agree; the bolts are not breaking they're loose because they are not
torqued to 75 ft lb. I'll bet dollars to donuts people use common Allen
wrenches to tighten these when they're laying under the coach and there is
no way you could apply enough torque with one of those!

Regards,
Rob Mueller
Sydney, Australia
75 - Avion - AUS - The Blue Streak
75 - Avion - USA - Double Trouble

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