Pinion Bearing Video

A

adrien genesoto

New member
Oct 11, 2008
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What I see from your video is three items that need attention.

1. The pinion may have lost the bearing preload, which can cause tooth chip, the pinion seal and trans
seal to leak oil from the weep hole, and it could also brake the tail end of the trans output shaft.
From the look of the pinion ring tooth wipe, the pinion should be a little deeper to center the wipe
on the ring gear, pinion preload may take care of that.

2. As is the the ring gear has too much backlash (0.004 to 0.006), the pinion input wobble (loss of preload)
could be a cause of the increased backlash and tooth chip.

3. The ring gear tooth chips are not a cause for replacement (IMO). With a small grinder dress up any sharp
edges, they are on the load side of the tooth. If the pinion has also chipped tooth, it could change the
equation.

The service manual has the settings.

--
Adrien & Jenny Genesoto
75 Glenbrook (26-3) Mods LS3.70 FD / Reaction Sys / 80mm Front&Intermidiate / Hydroboost / 16" Tires / Frame Rebuild / Interior Rebuild
Yuba City,Ca. Text 530-nine-3-three-3-nine-nine-6
 
Corey,

I have interesting and some inconvenient things here.
The guy that used to build the final drives for JimK lives in Plain City. His phone number is in the GMCMI roster. He does not seem to be listed in
be listed in the GMC Assist list. You might call him and he may still be north. That would be Walt Halley, I bet you could talk to him. He had a
good reason for giving up that work, he no longer has the tools but he can probably tell just how much trouble you are in.

The guy that is currently doing this work lives north of Detroit, but he is on a cruise through the Panama Canal and is not expecting to be home until
24th of this month. I don't even know when he will be back in cell phone range.

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Adrean,
I would love to talk with you.
Call me at 510-742-1101

On Sun, Mar 8, 2020 at 11:33 AM Matt Colie via Gmclist <

> Corey,
>
> I have interesting and some inconvenient things here.
> The guy that used to build the final drives for JimK lives in Plain City.
> His phone number is in the GMCMI roster. He does not seem to be listed in
> be listed in the GMC Assist list. You might call him and he may still be
> north. That would be Walt Halley, I bet you could talk to him. He had a
> good reason for giving up that work, he no longer has the tools but he can
> probably tell just how much trouble you are in.
>
> The guy that is currently doing this work lives north of Detroit, but he
> is on a cruise through the Panama Canal and is not expecting to be home
> until
> 24th of this month. I don't even know when he will be back in cell phone
> range.
>
> Matt
>
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
To be correct the trany output shaft shouldn't wobble that much, if the pinion has no side play it may be usable
as is. Guru Manny would be the ultimate word on this. Right now the trans case is room temp with that amount of play, it would be interesting to
recheck that shaft side play at operating temp.

Try to get a plug with a magnet, or put a magnet on the outside of the cover. Now is the time to add a drain plug.
Hope this has help you.

> Adrien/Matt,
>
> Thank you for the replies. I went ahead and got the FD out the the pinion is SLOPPY. Moves side to side quite a bit. Matt- I got in touch with
> Walt and while he no longer has the tools, he did have an extra 3.07 unit lying around. We are going to trade since he only needs it as a core. That
> way I can at least get this thing on the road and decide if/when I want to upgrade to one of the higher ratios at a later date.
>
> I know there is concern that if the pinion bearing is loose, there is a risk to the trans output. There is a MINISCULE amount of play as seen in
> this video: https://youtu.be/DqV15SPho1k
>
> Is this anything to be worried about?

--
Adrien & Jenny Genesoto
75 Glenbrook (26-3) Mods LS3.70 FD / Reaction Sys / 80mm Front&Intermidiate / Hydroboost / 16" Tires / Frame Rebuild / Interior Rebuild
Yuba City,Ca. Text 530-nine-3-three-3-nine-nine-6
 
We rebuild several. Units a month and find most of the pinion main bearing
shot .
We replace ALL the bearings.
Since we warranty them for 80,000 miles our people know what is critical .
Lot of the cores we get back have issues that require slight modification
before we can rebuild them.
I’m surprised we were not contacted about this as we are the major
rebuilder and supplier of the Final Drive units and LSD .
Should visit our web site and see portion of what we do.

On Tue, Mar 10, 2020 at 12:01 AM Adrien Genesoto via Gmclist <

> To be correct the trany output shaft shouldn't wobble that much, if the
> pinion has no side play it may be usable
> as is. Guru Manny would be the ultimate word on this. Right now the trans
> case is room temp with that amount of play, it would be interesting to
> recheck that shaft side play at operating temp.
>
> Try to get a plug with a magnet, or put a magnet on the outside of the
> cover. Now is the time to add a drain plug.
> Hope this has help you.
>
>
>

> > Adrien/Matt,
> >
> > Thank you for the replies. I went ahead and got the FD out the the
> pinion is SLOPPY. Moves side to side quite a bit. Matt- I got in touch with
> > Walt and while he no longer has the tools, he did have an extra 3.07
> unit lying around. We are going to trade since he only needs it as a core.
> That
> > way I can at least get this thing on the road and decide if/when I want
> to upgrade to one of the higher ratios at a later date.
> >
> > I know there is concern that if the pinion bearing is loose, there is a
> risk to the trans output. There is a MINISCULE amount of play as seen in
> > this video: https://youtu.be/DqV15SPho1k
> >
> > Is this anything to be worried about?
>
>
> --
> Adrien & Jenny Genesoto
> 75 Glenbrook (26-3) Mods LS3.70 FD / Reaction Sys / 80mm
> Front&Intermidiate / Hydroboost / 16" Tires / Frame Rebuild / Interior
> Rebuild
> Yuba City,Ca. Text 530-nine-3-three-3-nine-nine-6
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
> Jim- to be honest we haven't even had this thing on the highway yet. I want to get a 3.07 FD back in there to see what we are working with before
> making the decision on what gears to go with and spending the $$. At that point I would likely reach out.
>
> I will likely want to flat tow a Jeep Wrangler TJ (3,500 lb) at some point so I'm thinking 3.70 gears might be in our future.

Corey,

While I like your plan to get it right and then change things, I can tell you right now that the 3.07 put in there at the factory was wrong then.

Doing what you are doing is a good plan, it will only cost a set of drive axle screws and a gasket to find out what it should be like. Many people
have towed with the 3.07FD, but I bet you would like the 3.70 more. The experience can't hurt.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
> Not to go down another rabbit hole, but in my infinite wisdom, new drive axle screws were installed just 2 weeks ago after replacing cv boots.
> Torqued to 65 left, loctite etc. Since then the coach has driven about one mile. Do these bolts need replaced again? Do they stretch when you
> tighten them for the 1st time?

Corey,

That is a very valid question. Unfortunately, without knowing a lot more, nobody can answer it.

Forty plus years ago, the OE fasteners were supposed to yield during install as that was a factor to keep them from loosing tension in service.

If you really want to know, when you get the old screws out, sit down with a rag and a beer and compare by locking the threads of both old and new
screws together against a light or bright white surface. If the two don't fit together PERFECTLY, then the fastener has yielded. If they have
yielded, they are scrap. If you cannot detect any yield, they are probably safe to reuse. You MUST inspect each of them against a new fastener.
This is because the torque/tension relationship had a 35% scatter. So, just because one shows no yield does not mean that the next one is still good.


After my recent go rounds, I have about a coffee can full to clean and inspect. I'll get to it some day.

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Cory, on those bolts we have great result reusing the bolt and washer by
cleaning them and using Blue LocTite.
Keep in mind the driver side will vibrate more as it is mounted to the
Spider gear.

On Wed, Mar 11, 2020 at 8:41 AM Matt Colie via Gmclist <

> > Not to go down another rabbit hole, but in my infinite wisdom, new
> drive axle screws were installed just 2 weeks ago after replacing cv boots.
> > Torqued to 65 left, loctite etc. Since then the coach has driven about
> one mile. Do these bolts need replaced again? Do they stretch when you
> > tighten them for the 1st time?
>
> Corey,
>
> That is a very valid question. Unfortunately, without knowing a lot more,
> nobody can answer it.
>
> Forty plus years ago, the OE fasteners were supposed to yield during
> install as that was a factor to keep them from loosing tension in service.
>
>
> If you really want to know, when you get the old screws out, sit down with
> a rag and a beer and compare by locking the threads of both old and new
> screws together against a light or bright white surface. If the two don't
> fit together PERFECTLY, then the fastener has yielded. If they have
> yielded, they are scrap. If you cannot detect any yield, they are
> probably safe to reuse. You MUST inspect each of them against a new
> fastener.
> This is because the torque/tension relationship had a 35% scatter. So,
> just because one shows no yield does not mean that the next one is still
> good.
>
>
> After my recent go rounds, I have about a coffee can full to clean and
> inspect. I'll get to it some day.
>
> Matt
>
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
Evening,
I'm sure Jim K will back me up on this if your pinion bearing allows to much tilt under load you can pop the side out of the output shaft in the
tranny, been there done it, no fun. Remember these are male and female splines about an inch long mated and they have pretty close tolerances, not
much wiggle room. It's not like on rear wheel drive vehicle that had the driveshaft so you don't at least waste the tranny. Just speaking from
experience.
Skip Hartline
--
74 Canyon Lands, FiTech,
3.7 FD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
 
That is why I prefer to r & r the transmission/final drive as an assembly.
Much easier to have it up on a sturdy bench and separate the two. I like
handling the final drive on a cherry picker where I can make very, very
sure not to damage the seals between the two, as well as the gasket. I have
done it in the coach, only to have to separate the two a second time to fix
what I screwed up wrestling that heavy final drive into position. There
ain't much wiggle room in there.
Jim Hupy
Salem, Oregon

On Sun, Mar 15, 2020, 3:30 PM Skip Hartline via Gmclist <

> Evening,
> I'm sure Jim K will back me up on this if your pinion bearing allows to
> much tilt under load you can pop the side out of the output shaft in the
> tranny, been there done it, no fun. Remember these are male and female
> splines about an inch long mated and they have pretty close tolerances, not
> much wiggle room. It's not like on rear wheel drive vehicle that had the
> driveshaft so you don't at least waste the tranny. Just speaking from
> experience.
> Skip Hartline
> --
> 74 Canyon Lands, FiTech,
> 3.7 FD, Manny Tranny,
> Springfield Distributor,
> 2001 Chevy Tracker Ragtop Towd
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
So many of the cores we get back are in poor shape in more ways

On Sun, Mar 15, 2020 at 3:59 PM James Hupy via Gmclist <

> That is why I prefer to r & r the transmission/final drive as an assembly.
> Much easier to have it up on a sturdy bench and separate the two. I like
> handling the final drive on a cherry picker where I can make very, very
> sure not to damage the seals between the two, as well as the gasket. I have
> done it in the coach, only to have to separate the two a second time to fix
> what I screwed up wrestling that heavy final drive into position. There
> ain't much wiggle room in there.
> Jim Hupy
> Salem, Oregon
>
> On Sun, Mar 15, 2020, 3:30 PM Skip Hartline via Gmclist <

>
> > Evening,
> > I'm sure Jim K will back me up on this if your pinion bearing allows to
> > much tilt under load you can pop the side out of the output shaft in the
> > tranny, been there done it, no fun. Remember these are male and female
> > splines about an inch long mated and they have pretty close tolerances,
> not
> > much wiggle room. It's not like on rear wheel drive vehicle that had the
> > driveshaft so you don't at least waste the tranny. Just speaking from
> > experience.
> > Skip Hartline
> > --
> > 74 Canyon Lands, FiTech,
> > 3.7 FD, Manny Tranny,
> > Springfield Distributor,
> > 2001 Chevy Tracker Ragtop Towd
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
It totally amazes me that a final drive that was engineered to move a 4000#
automobile can reliably drag a 12,000 pound motorhome down the road at 70+
mph for 100,000 miles and farther without giving trouble. Speaks well for
GM engineers of the day.
Jim Hupy
Salem, Oregon

On Sun, Mar 15, 2020, 10:20 PM Jim Kanomata via Gmclist <

> So many of the cores we get back are in poor shape in more ways
>
> On Sun, Mar 15, 2020 at 3:59 PM James Hupy via Gmclist <

>
> > That is why I prefer to r & r the transmission/final drive as an
> assembly.
> > Much easier to have it up on a sturdy bench and separate the two. I like
> > handling the final drive on a cherry picker where I can make very, very
> > sure not to damage the seals between the two, as well as the gasket. I
> have
> > done it in the coach, only to have to separate the two a second time to
> fix
> > what I screwed up wrestling that heavy final drive into position. There
> > ain't much wiggle room in there.
> > Jim Hupy
> > Salem, Oregon
> >
> > On Sun, Mar 15, 2020, 3:30 PM Skip Hartline via Gmclist <

> >
> > > Evening,
> > > I'm sure Jim K will back me up on this if your pinion bearing allows to
> > > much tilt under load you can pop the side out of the output shaft in
> the
> > > tranny, been there done it, no fun. Remember these are male and female
> > > splines about an inch long mated and they have pretty close tolerances,
> > not
> > > much wiggle room. It's not like on rear wheel drive vehicle that had
> the
> > > driveshaft so you don't at least waste the tranny. Just speaking from
> > > experience.
> > > Skip Hartline
> > > --
> > > 74 Canyon Lands, FiTech,
> > > 3.7 FD, Manny Tranny,
> > > Springfield Distributor,
> > > 2001 Chevy Tracker Ragtop Towd
> > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk
> http://www.gmcrvparts.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
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