DIY: Fix Your Leaking Differential

Well, my car axle seals seemed like that too. But there was no stains around them, so I guessed that it could be anything but a leakage. Air flow would drag diff fluid to some place down there, but simply there were none.

So I cleaned it up with some cloth soaked with diesel, and after 500 miles, it is still clean.

Sorry, if you're not meaning the axle itself, but the area around, then you may have a leaking seal.

About the driveshaft, there's no problem on disconnecting from the gearbox. Just number all the bolts and nuts to return them to same place, and be careful on lowering it. Better if you have another person to help you holding it, but you can do it with jack stands or wooden blocks by yourself.

Theodore thank you for this informative DIY! I'm starting to chronicle the process of installing an OS Giken differential - LINK to Thread - and will be utilizing some of your tips here. I'm curious if you happen to know the differential carrier bearing/race part numbers for our diffs? Any other tips you have for me would be greatly appreciated as well.

I don't think BMW sells those parts separately. You can buy them from the aftermarket and one of those companies also made this video that might be helpful:

Great write up need to do the job. Is it recommended to get new torx diff bolts for this job? Do only cars built 09 and before use the counter balance bolts? Do they need to be torqued in a star pattern? Also how do you reinstall the nut flange?

can someone explain the purpose of counting the threads? wont it count 10 rotations regardless of how you put the nut back on? great write up OP

Just did the pinion seal job today. What a pain in the ass to remove the full exhaust and shielding, etc. I do have one concern. I did find on black bolt of the 6 securing driveshaft to the pinion. I made a mistake my not marking the bolt all the way down to the pinion.

My pinion is marked blue, that means it has a black bolt. BMW tis says to line up the black bolt with the mark however the mark on my pinion is in the middle of the two bolts and not exactly lines up seen below. The only logical place to put the black bolt was where I put it.

Road test went smooth, no sound from drivetrain at all but still curious to hear your thoughts here.

Thanks all for this thread, wrapped up an axle seal today. Some tips for those who are mechanically squeamish:

Removed the output flange using two pry bars on opposite sides. Lots of force. It doesn't move little by little, it just lets go, so apply force until it releases.

Removed the output cover by twisting it loose after bolts are removed, then following with pry bar around the sides, just like the racing diffs video shows.

Knocked out the old seal with a screw driver and hammer just fine. Took lots of force.

I didn't find much about getting the seal seated evenly and not crooked, but it wasn't trivial and eyeballing it wasn't working. I ended up making a feeler gauge to go behind the seal between it and the lip on the inside of the output cover: felt good with a distance of 7.5mm between seal and lip. Hammered the seal in using a piece of 2.5" pipe. Lots of force again.

The oil hole location is marked on the output cover by a yellow dot. Point the yellow dot to the upper left. This is for the right side output.

When reinserting the output flange it will stop twice. Once when just getting it to go in intially, and again with about 1 inch to go. Guessing that's the lock ring. Gotta push through it with some force.

I’m going to try out the upgraded pinion seal from Corteco available from FCPEuro. I’m thoroughly convinced it will outlast the chap, weak bullshit BMW pinion seal. There are two extra seal lips to go through and a bigger, more durable spring.

Had a machine shop open up a Miller 8891 installer to accommodate the extra lip on the seal