Hey guys, hope you’re doing well. Unfortunately my car has a leak between the driveshaft & the differential, I believe I’ll have to replace the pinion seal with a new one to stop the leak.




It’s a 2002 T/A WS6 A4 20K miles, stock GM 10 bolt rear end & 3.23 gears. I don’t use the car that much (once a week) I noticed a couple of drops on the floor a week later before driving it again.

Now, is the GM OEM 12471523 pinion seal my best bet ? And what do I have to keep in mind when doing this fix? Because I won’t be the one doing the repair, I’ll have to take it to a reputable shop.




when changing the gear oil with Lucas 75W90, I know I won’t need to add the additive like the manual says because it’s a Torsen diff. I’ll just make sure it’s a synthetic oil (75W90)






regarding installing the diff cover, do I add sealant like RTV to the gasket to avoid any leaks? And what gasket would you recommend (Felpro maybe) ? I’ve been thinking about getting an upgraded diff cover from hawks motorsport with a drain plug to make things easier (I got UMI rear sway bars so I don’t know if the sway bar will clear the upgraded diff cover)



I live overseas in UAE 🇦🇪 and I have to order the parts online so I have to make sure it’s the right part.

I appreciate your help. Thank you.

 

Looks like you are on the right track. The trick to successfully replacing the pinion seal is to maintain bearing preload when re-assembled. Short of complete disassembly and re-assembly with a new crush sleeve, mark the pinion nut WRT the pinion and to be sure that nut is lined-up with the mark when put back together. "Theoretically" this maintains proper pinion bearing preload. Be sure to check the yoke for wear grooves and polish those out if any prior to slipping the yoke back onto the pinion (don't forget to clean and coat the seal surface with lube to avoid damage to the seal).

Replacing the cover with one w/ a drain plug is a good idea (might as well get one that has the adjustable bolts that support the carrier gears), however I can't advise which covers fit your aftermarket sway. For sure, coat both sides of the gasket w/ RTV (Permatex black is my go-to). Let it set up ~ 6 hrs before adding lube.

 

Having done this on a 2002 Z28 2 years ago,had to get two seals, the 1st one ordered/received had a 'pinch' on the sealing surface that crested a large potential leak. Upon removal of the yoke off the pinion (did not come off with the normal ease, had to be moderately hammered off), the splines were filled with some white hard cement and had to be 'picked' off. Evidently GM used this cement to seal the splines and keep the fluid from leaking out thru the splines.
Since it's sitting at 20,000 miles, it probably doesn't have the proper preload anymore. We kept tightening the nut until I felt the preload was proper.
The end result was a good rebuild with no leaks and ran quiet.

 

I thought the 2002 differentials were auburn? I could be wrong but you’ll know when you get the cover off. If you see springs it’s an auburn with clutches

 

98s' got Auburn, 99 and later got Torsen.
Some SSs' and TAs' could have got an Auburn as an option at SLPs' facility for those vehicles.

 

Thank you so much for the above info.

I believe mine is a Torsen Diff, but thank you for sharing the pic above to determine the difference between them.

Yup that’s exactly what I thought as well 👍 thank you for sharing

 

I appreciate you taking the time to help me with this brother.

so you’re saying I’ll need to get a new crush sleeve as well when changing the pinion seal, if so then which one would you recommend? I found a GM one for sale on EBay.




many thanks

 

To just fix the yoke seal, a new crush sleeve is not mandatory if the pinion nut is put back on exactly as it was before disassembly. The absolute best way to ensure your pinion bearing preload is where it needs to be is to replace the crush sleeve (and the one you found looks to be correct) and re-establish the pinion bearing preload. However much more disassembly of the rear may be required to swap out the crush sleeve as I'm not positive it can be removed through the front yoke opening without taking the entire pinion out........which can only come out through the back which requires the differential to be removed too. But once you go that far, you might as well replace all bearings and seals at the axle ends while you're at it.

 

Got it 👍 much appreciated, I found this video on YouTube which explains how to do it the same you explained on your first reply. But regarding the 4 bolts that hold the driveshaft, I’m not sure to how much I need to retorque them back to ( in the video he thinks it’s 18ft/lb ) and the nut that’s in the yoke will be fine as long as I mark everything and count the threads that are visible before taking everything out (what I meant was I don’t need to retorque the nut when putting it back on, right?)

I also wanted to make sure that the pinion seal pic is the one designed for the 2002 models (2nd design)

 

You will need to apply sufficient torque to get the nut back into its position it was in before you took it apart. This won't be a "measured" amount of torque, it will be whatever amount of torque it takes.

During normal assembly (when crushing a new sleeve), it takes quite a lot of torque on that nut to crush the sleeve enough to get the pinion bearing preload right (not measured by torque applied to the nut, rather by measuring how much torque it takes to spin the pinion with the diff carrier out.......... IIRC, its around 15-25 in-lbs to spin the pinion). The vast majority of force that results from stretching the pinion goes through the crush sleeve and inner bearing races and clamps them all together so that the inner races never spin WRT the pinion; a small amount of that left-over "pinion-stretching" force is applied to the pinion bearing races as preload. As you can imagine, as the pinion nut is tightened, once the bearing preload starts increasing from zero, it doesn't take a lot of nut rotation to go from too little to too much bearing preload. So be careful to not go past that point otherwise you WILL need to replace the crush sleeve (as it will have been crushed too much and won't be able to maintain sufficient inner race clamping force.....or the pinion preload will be too high and result in premature wear).

In your situation, you are just trying to get it put back together the same way it came apart (and are forced to assume nothing else changes dimensionally), thus marking the nut's position WRT the pinion. It is still important to verify that that there is no play in the pinion once this is achieved, and that the pinion preload (torque needed to spin the pinion) seems reasonable (if the diff carrier is still installed, it will be much more than the 15-25 in-lbs noted above). In fact, now that I think about this more, if the diff carrier remains installed, it's not a bad idea to measure how much torque it takes to spin both the pinion and diff carrier / axles (wheels in the air) BEFORE disassembly to give you a target torque value to shoot for when re-assembled. Use caution as any additional drag caused by axle bearings and rear brakes will only increase the amount of torque it takes to spin everything and muddies the water further.

Good luck.

 

Hey guys, just a quick update on this thread.

I got the OEM pinion seal installed at the shop and test drove the car and there were no issues or vibration during the test drive, I left it at the shop overnight to see if there will be any leaks and I also installed the TA performance Diff cover.

I’ll keep you all updated, Many Thanks

 

Awesome, thanks for updating this thread with your final solution. Fingers crossed you fixed the leak.

 

thanks brother 👍 and thank you for your help.