[eddieboy510]

So how common is it for the rear differential pinion seal to leak? I changed the rear differential fluid on my 328i e90 2008 with 80k miles on it. now i have drips in my driveway for 2 weeks now.crawled underneath and its spitting fluid from the driveshaft pinion slinging it all underneath. I smell the fluid burning up on the exhaust and its annoying. I already purchased a new differential with 60k miles on it for 80$ on Ebay. I guess my question is should I just install the used differential or have the seals replaced on that one then install? kind of going back and forth on it just wanted to know some other opinions.

[eddieboy510]

Thanks for reading anybody have an opnion on this now 21 views come on guys thats why we are here on forums for questions answers thoughts and opinions.

[Biginboca]

It's been 2 hours dude you need to chill.

If 21 people read and didn't answer it's cause they, like me, aren't sure of the answer. You want answers from people who aren't sure if they are right?

Ok fine here's one. I bought a used Diff and swapped it in without changing seals. It hasn't leaked in 2k miles since the swap. So I say if the used Diff is not leaking before install then run it. But I don't know if I'm right...

[eddieboy510]

thats exactly what im looking for. experiences and opinoins. Thanks for your input. not necessarily looking for right answers just thoughts and opinions. Yours is valued. THANK YOU

[CTinline-six]

I know this is a long shot, but maybe worth the $20 for fluid. My Jeep Cherokee XJ (my offroad weekend toy) had a leak from the front pinion seal on the rear differential. I swapped the diff fluid with Redline 75w90 thinking I would get to the seal eventually, and it has been dry ever since. I checked the fluid level to verify it is full. I've read it's because Redline has a different kind of base oil? Not entirely sure.

This might not help if you have a large leak, but it might be worth throwing some in the new/used diff. I did this for the front differential which had a small weep around the pinion, and it has dried up as well.

[Biginboca]

For the record I did change the fluid when I installed my used Diff. I used the BMW factory Diff oil.

[CTinline-six]

Originally Posted by Biginboca

For the record I did change the fluid when I installed my used Diff. I used the BMW factory Diff oil.

I'm curious who makes the factory differential fluid. I know the BMW 5w30 oil is produced by Shell.

[andy_06xi]

My 2006 330xi needed a new diff pinion seal at around 105K miles. I'm taking in my wife's 2014 X3 this morning to have its pinion seal looked at -- leaking and smell from hitting hot exhaust. So I'd say this is common for BMW -- who seemingly can't make gasket and seals that don't leak.

[juld0zer]

Once upon a time they specified SAF-XO which is a Castrol product. These day it is referred to as OSP. I imagine it is from a European producer

[Efthreeoh]

So you bought a used diff off of eBay because the diff in your car sprung a pinion seal leak? Are you installing the used diff DIY, or at a shop?

[eddieboy510]

yeah DIY i figured i would either just swap it out or rebuild the bought used differential and still swap it out myself.
whenI went to change the fluid it was bone dry. Two days before i changed the fluid it was making a whirrling sound. so I dont know maybe it has more damage than just the leak. but since that day hasnt made any other sounds and still feels and drives like normal. Plus i got the used differential for a great deal and could probably sell the one that is on my car and break even

[mweisdorfer]

I did a quick search on this forum for differential leak and only 3 posts even shows up. Yours is one of them.

Aside from that prior to doing a search, my inclination was that differential leaks on e90's are fairly rare.

I have 143,000 miles on my e90 335i. It has never leaked. I have changed the oil out 2x in that time span.

[desertman123]

Oh you should 100% press new seals in. I bought a used 06 325i diff off ebay and it pissed out the axle flange seal - coated my entire rear end as it flung oil.

[6ixSpd]

Don?t worry, the leaking is just a self-lubricating anti-corrosion protection.

[max_330i]

I bought a used rear diff with a 3.64 final drive ratio on eBay as a cheap performance mod (shorter gears = more torque to the wheels). I had my indy install it with fresh fluid, junked the old one, and called it a day. If the second one you bought has good seals and no leaks, I don't see a reason to mess around with the original diff. YMMV

[juld0zer]

Originally Posted by 6ixSpd

Don?t worry, the leaking is just a self-lubricating anti-corrosion protection.

Good one haha

Maybe you guys got better seals in NA?
Over here i see leaky diffs even on the new F cars. Never seen one leak that much through the pinion seal to cause noise though.

What type of prop shaft do you have OP? Bolted or inserted (50mm nut)?

[BB_cuda]

Changing pinion seal is no walk in the park. The pinion gear has to be removed and the pinion bearing changed as well. Axle seals aren't that big of a deal to change. I had my diff converted over to limited slip Wavetrac and got new axle seals. The pinion seal was not touched. No leaks so far and i've driven about 4000 miles since switchover.

The ebay diff might be the easiest thing to do provided it doesn't have a pinion seal leak too. Hopefully you got the exact same diff with same ring to pinion ratio so that you run the same rpm for a given speed. good luck

[juld0zer]

It's not that bad. You don't have to remove the pinion gear, not even on the inserted propshaft type diff. Ideally you'd do the job on a hoist with the special tools to counterhold the pinion via the splines but i imagine a well adjusted handbrake or assistant standing on the footbrake may work also. The inserted propshaft version is extremely tight. The threadlock compound used is almost a glue - which must also be used on reinstallation.

You just need to remove the pinion/input flange:
- Bolted propshaft diff: Undo bihex nut which holds the flange on
- Inserted propshaft diff: Heat up the huge bihex nut and release it.

The important thing is to MARK the nut relative to the pinion and use a depth guage as a backup to determine how tight to do it all up afterwards. This sets the preload and the measurement and marking allows you to restore the same preload after the repair.

If you're not afraid to do a sump gasket then this is similarly challenging, but will require a lot more muscle.

[BB_cuda]

Originally Posted by juld0zer

It's not that bad. You don't have to remove the pinion gear, not even on the inserted propshaft type diff. Ideally you'd do the job on a hoist with the special tools to counterhold the pinion via the splines but i imagine a well adjusted handbrake or assistant standing on the footbrake may work also. The inserted propshaft version is extremely tight. The threadlock compound used is almost a glue - which must also be used on reinstallation.

You just need to remove the pinion/input flange:
- Bolted propshaft diff: Undo bihex nut which holds the flange on
- Inserted propshaft diff: Heat up the huge bihex nut and release it.

The important thing is to MARK the nut relative to the pinion and use a depth guage as a backup to determine how tight to do it all up afterwards. This sets the preload and the measurement and marking allows you to restore the same preload after the repair.

If you're not afraid to do a sump gasket then this is similarly challenging, but will require a lot more muscle.

Maybe it's embedded and i didn't catch it. I did change the outer packing (blue rubber) and a new 50 mm nut on my 215 case. Are you talking about removing the wierd bihex behind the 50 mm nut? Some pictures here would be wonderful. Sorry to take over, eddie.

Finally, i wasn't clear on if the pinion bearing comes out the front or if the pinion bearing is even involved in what you suggest. Please elaborate. The probelm i've found is it is difficult to buy a replacement pinion bearing. If your method doesn't remove (or unload that bearing), all the better.

Comment: I did have a tough time breaking loose the 50 mm nut. I finally learned that after turning it a a couple revolutions that turning opposite direction back towards tightening it broke loose the blue crusty thread locker. It was easy to turn after learning this trick. Here is my DIY over on another board for the whole diff swap job.
http://www.e90post.com/forums/showthread.php?t=1355219

[juld0zer]

Correct, to do the pinion seal on the inserted type diffs (no guibo on diff end, no uni joint), you need to release the bihex nut behind the 50mm nut. No removal of the bearings is required.

To do the pinion bearing you first have to source the bearings. After realising how difficult they are to find, you resort to fitting a new or donor diff. I've never replaced bearings in a BMW diff. In fact, they discourage it by not even listing any instructions for the repair.

The 50mm nut and the rubber cover must be replaced each time it is disturbed.