View Full Version : Rear transmission is oily...

10-11-2004, 12:26 PM
Was up under the back end of the car yesterday, flushing brake fluid and changing some rotors, noticed an abnormal amount of grime all over the rear transmission...

is this normal?

The CV boots on the rear axles were solid and uncracked, so I figured the grime was from the tranny itself...

It wasn't dripping, persae, but it was grimy for sure.

10-11-2004, 12:47 PM
Are you saying that the rear diff is oily or the rear or the transmission is oily?

10-11-2004, 01:01 PM
The box that the axles run into. I suppose it could be considered the rear diff...

10-11-2004, 01:25 PM
mine too. think it's the seals. how much of a pain are they to change?

10-11-2004, 01:51 PM
its normal to be oily...

10-11-2004, 02:50 PM
It depends on which side is oily if it's the side with the exhaust it'll be more of a pain in the ass because you'll have to drop the exhaust to get at the CV-Joint. It's not that hard of a job to change the seal which is what's causing the leak just takes a while to do, you'll need to drain the differential fluid before you start. The part is only about $3 plus the cost of new gear oil, but having it done my a shop will cost about $200 with labor I did mine one weekend and saved about $150.

10-11-2004, 04:15 PM
I did both of mine in Feb. this year.

It's not the hardest job in the world but, it is time consuming.

The seals are about $5 ea. from most places (ECS, Germanautoparts, Impex etc...).

There are 3 different seals.

The 2 that go on the axle shaft flanges and the one that goes on the driveshaft input flange.

Typically, the axle flanges are the ones to go bad. I only had to do my driver's side seal but, I did both for the heck of it.

You need the following tools to do the job:

12pt (triple square) bit - http://www.germanautoparts.com/main2.php?action=Tools&input%5Bmodel%5D=Audi&input%5Bmaingroup%5D=Axle+%26+wheel+bearing+tools&input%5Bsubmit%5D=Submit

A seal puller - http://www.thetoolwarehouse.net/shop/LIS-56750.html

6mm hex key/socket - http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00942676000

10mm hex key socket (opens diff filler and drain plugs) - http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00942679000

You also will want to empty the diff before replacing the seals, otherwise it will leak all over the place. You can use a GL-5 rated gear oil. I went with Redline 75W90. You'll need 1.9Qts.

Here's the procedure:

1. Drain rear diff by opening filler plug and drain plug with a 10mm hex key socket. Replace drain plug when empty.

2. Start loosening drive axles at the flanges on the rear diff. Use an 8mm 12pt. bit to loosen the bolts. Always make sure the bit is fully seated before turning on each bolt.

3. Once axles are free from the flanges, you may need to push the wheels upward into the wheel wells with a floor jack to give the axles room to move away from the flanges. The exhaust pipe won't be a problem. Beware! There's grease inside those axle flanges!

4. Use the 6mm hex key socket to loosen a bolt hidden in the center of each flange. There will be grease covering the bolt heads (extremely messy work!).

5. Remove flanges and then use seal puller to pry old oil seals out of diff. Try not to scratch metal surfaces, they are meant to be tight seals.

6. Once old seals are out, use a large socket and a hammer to gradually tap the new seals into place. Tap them in until they are flush.

7. Re-install flanges, axles and axle flange bolts.

8. Pump 1.9Qts of gear oil into diff. and install filler plug.

9. Drink beer and curse at old seals!

The End.

10-11-2004, 04:46 PM
not to hijack the thread or anything, but how do you check/top-up the gear oil in the front and rear diffs? Mind you, this is a blind question as I haven't looked under there yet to really see what it's like. Just a quick explanation would be great. I am very familiar with the way diffs are setup, just not this particular one. Is it the same as most?