JamesC

iTrader: (5)

From big gear head: A leak isn’t always caused by the seal. Bad pinion bearings allow the pinion to run off center, which causes the seal to be too tight on one side and too loose on the other, thus causing a leak. A loose pinion nut will do the same thing because it allows the bearings to be sloppy and to run off center.

If the seal itself is bad, note the following information.

Be prepared to lose some gear oil.

1. To reach the seal, yank the drive shaft (I’d mark the U-joints and yoke in order to put the shaft back as it was).

2. Remove the pinion nut and yoke. An impact gun will be helpful in removing the former. The yoke may require either a puller or a tap or two with a dead blow hammer.

3. Remove the seal with an appropriate prying tool.

4. Clean the “housing” where the seal sits as well as the splines of the yoke.

5. Smear a little RTV sealant into the “housing.” Lube the new seal’s rubber lip with clean gear oil to prevent burning.

6. Install the seal (Timken 7457N) by lightly tapping it in, working around the seal evenly until it’s seated.

7. Smear RTV on the splines of the yoke so that oil doesn’t seep through them, then install the yoke. DO NOT put RTV on the splines of the pinion shaft itself. Doing so will push the sealant into the outer pinion bearing and cause major problems.

8. Use a new pinion nut (GM 1260823) and red Loctite (as the nut can eventually back off). Torque the nut to 150 ft. lbs.

big gear head: I’ve checked the pinion bearing preload on rear ends before disassembly and then installed a nut and torqued it to different amounts to verify where the pinion bearing preload changed. Usually it was 200 ft. lbs. before the preload started to increase, so 150 should be safe. This will be tight enough both to keep the nut from backing off and to keep the bearings tight.

9. Re-install the drive shaft.

10. Check the fluid level.

Note that if the bearings are being replaced, a new crush spacer should be used and torquing the nut to 150 ft. lbs. will not work. The bearing preload must be set in this case.

I’ve compiled much of the above information from big gear head’s various posts on the subject.

Instead of torquing to 150 ft. lbs., others have used the “scribe” method: Put a scribe mark on the pinion nut and the pinion threads. Then before removing the pinion nut, count the number of threads that protrude beyond the nut. After removing/installing the seal as above, tighten the nut until the scribe marks line up and the thread count is the same as it was before removal. Re-install with red Loctite on the pinion threads.

Note the following provisos to the "scribe" method: According to big gear head, first, if the leak has occurred because the nut has backed off, there is no true reference point to scribe. Second, if one yoke replaces another, the thickness of the yokes will nearly always be a bit different due to machining tolerances; as a consequence, counting threads may not work because the nut won't be in its original location. Third, a new nut should be used for best results.

If members have thoughts or advice on the subject, please feel free to contribute.

JamesC

jmd

iTrader: (4)

Looking good, James.
Keep reminding me to fix the small leak on one of mine. Maybe it'll get done.

UNCLE TOM

iTrader: (1)

your post is almost word for word the way i did mine a few months back . (i know , great minds travel in similar circles) i was unable to get a new nut and only torqued to 120lbs. . but , so far so good . good post .

jakemussman

iTrader: (3)

Great Info! I need to check out whats causing the leak on mine. Its deffinitely from the pinnion seal area. Lucckily its not to bad because I have my hands full with swapping my interior, and on top of that when i pulled my carpet I discoverd that I have a small heater core leak.

torque_is_good

old timer here counts the threads and that's how I just did it on my 3rd gen.

Keoman

iTrader: (3)

Good!

I have a question. I have hit the pinion nut with an impact hammer on full blast and the dam thing still wont budge. The housing is currently out of the car and i have no way of holding the pinion gear in place and loosening the nut!

Also, do you have any information about how to set the "bearing preload"?

Need suggestions!

Thanks

keo

big gear head

Use a very large pipe wrench to hold the yoke. Setting the bearing preload is covered in this https://www.thirdgen.org/forums/tran...axle-gear.html

Keoman

iTrader: (3)

Horay for huge pipe wrenches!
Lets take this step by step now, how in the world do you get the yoke off?? I pounded on that thing for a good 10 minutes with different things and nothing. Some sort of puller? I think ill rent one tomorrow.

Much obliged.

torque_is_good

you won't catch me putting rtv with the pinion seal

count exposed threads, mark the nut if needed, count turns to remove the nut

remove seal

clean area

install new seal (note the lack of rtv)

replace nut counting turns and threads

you're done

I've done too many to remember this way

good luck

big gear head

OK, I've got to ask, why will you not use RTV on the outside of the pinion seal? Most of the time there are scratches in the housing from removing the old seal and the RTV seals the scratches to prevent leaks. Why would you not do this?

Sometimes I have to use a puller to remove the yoke. A standard puller like you use to remove the harmonic ballancer or steering wheel works fine.

torque_is_good

ahh, outside of the seal. Well, honestly, I've never seen where the inside surface has been hacked to the point where it leaks with a new seal. And for the inside, well, it's easy to see that rtv wouldn't stay put there.

1deepwillis

hey fellow BaddA%#BowtieBoyz.New here and got a question on which way to go with my reaar end.I have a 88 rs that was originally a v6,prior to my purchase a carbed 350 was put in it,tranny remained 700r4. The diff code in manual states it is std and not posi.I had recently purchased what i thought was a complete rear end from an older camaro,well the guy said it was posi but apparently he knew nothing bcuz instead of swappin em,he just changed the gears and when i got it back it was whining,now i need the pinion bearing replaced.i know where complete one at salvage off a 92 v6 is. 250pulled or a bearing&seal rep kit is 105 at autozone. labor to put new rear on is 225 would i need to do bearings?seals if i got the one from the salvage,what would be the best? and if it has posi culd i just take posi out and use it.Thanks guys in advance

ternandes

iTrader: (7)

Thanks as usual for an informative thread. I replaced the pinion seal on my 87 bird this past weekend... one note to others:

I jumped to this thread from the 10-bolt sticky, and assumed it was 10-bolt specific. The seal that is specified in the OP did not match what I had in my car... which turned out to be Timken and National P/N 8610.

blacksunshine'91

iTrader: (10)

I had the same part in my car also. What I found weird/confusing is that Rock Auto lists both the 8610 and the 7457N as applicable to my '91 GTA.

My question is why do we need to replace the pinion bolt?

big gear head

You mean the pinion nut?

The nut is a lock nut. Once it has been used it looses some of it's ability to stay tight. I've seen many pinion nuts back off after being used for a while. I always use red Loctite on the nut and I use a new nut whenever possible.

blacksunshine'91

iTrader: (10)

For those using the yoke GM upgraded to ~2000, the Timken 7457N and 8610 will not work. the inner seal is too small. The seal for that one from GM is 12471523.

The pinion nut has been superseded by GM p/n: 88891763.

Hope that helps anyone.

midias

Thanks for the info

firestorm

Do I have to use RTV on the yoke splines or will ptfe pipe sealant work?

big gear head

That will work too. I've used both. RTV is easier to clean off if you ever have to do it again.

Cadillacbart

So if I am using a four post lift, I should be able to just support the spring perches behind the axles to keep them from pushing down so I can safely unbolt the torque bar to get better access to the pinion flange, correct? No need to lift the car at all, except that it is sitting on it's tires on the lift ramps?

Cadillacbart

So I figured it out- i was asking a dumb question since you have to raise the car to let the axle drop far enough to get the torque bar bolts out.

Turns out it wasn't hard to replace the pinion seal with the torque bar in place, so that job s done.