TheAvgBear

I am trying to solve the issue of my atf leak. And i am slightly confused as to what is what exactly, and where fluids boundaries are where. In the image below I labelled the three sections under investigation.

1) Are sections/housing #1 and #2 collectively referred to as the transfer case or center differential? (or possibly front diff?) ... Or, is one section the transfer case? and the other is the differential?

2) I know that section #1 holds the gear fluid, bc of the drain and fill holes. I also recently replaced the output shaft seal. But what fluid is supposed to be in section #2? atf? or gear fluid? ... Does the atf stay and remain only in seciton #3?

3) Between #1 and #2 there is a paper gasket, but it looks like there is atf dripping from the bottom of both section #1 and #2?

3.5) If there is atf in section #2, is there another seal that could be leaking in between sections #1 and #2 to allow the atf to make it back that far?

4) is there a similar gasket between section #2 and #3 (the dealership says no)?

5) I recently learned that the front diff/final drive up front for the axles holds gear fluid as well. Is fluid in anyway connected with the fluid in section #1?



Sorry for the tedious post. I am getting ready to tear everything apart today and just want to know what to expect (first audi ive owned). My plan is to drop the exhaust, drain everything, disconnect the driveshaft, remove section #1 and replace the paper gasket, then remove section #2 and clean up the contact surfaces, find anything else that could be causing a leak. Then hopefully re-install everything nicely, top up the fluids and be done with it.

Has anyone else done a job similar to this? If so do you have any advice or insights to share? Thank you for your time.

TheAvgBear

Another update for anyone that may be reading: I have learned that there is ATF in sections #2 and #3, and gear fluid only in #1. I have also learned that there is a gasket between #2 and #3 (PN: 01v-321-381). The one between #1 and #2 is PN: 01V-321-381a. And that the final drive/front diff gear fluid does not mix with the center diff gear fluid.

After researching all day I spent a good hour under it this evening, cleaning absolutely everything. Then let it idle for ~20 min to see where exactly it was leaking from.

It looks like it is running down on the left (drivers) side of the boundary between sections #1 and #2, then down to the bottom to drip off.

Before idling, cleaned up:


After idling:
https://i.imgur.com/yCufmNA.jpg

Side view of the left / drivers side:


Another shot:


The puddle that formed after idling:


I am starting to become more familiar with the composition of the quattro drivetrain. But I dont understand why/how there is ATF fluid leaking over the gap between housing #1 and #2. The front face of section #1 (where it meets #2) is open, so the only thing that should leak through the paper gasket between them is gear fluid right? There is a breather ontop of #2, could atf be escaping through there and then down along that boundary b/n #1 and #2? Anything else I am not aware that could be causing this?

P4Ring

I would say torque converter seal but fluid would be comming from the bell housing Instead. While driving it would splash back all the way to the prop shaft. The whole transmission contain ATF. The transmission contain the front dif (front section) and the torsen dif (rear section). They both use the same ATF so basically fluid is everywhere.

Advice, if you plan to remove the prop shaft make sure you mark the original position before removal. This will prevent vibration due to rotation im-balance. Factory mark should be there, but to be safe make your own.

TheAvgBear

Thanks, will do. I am going to remove that and the whole diff housing, inspect everything there and replace the gasket. Hopefully solve the issue.

Any advice for removing that housing and working in and around the torsen diff?

thejulex

Do you even know what you are saying?
Have you done this before? Remove propshaft?
Are you reading the information about this from a book/CD?

Incorrect, prop shaft can be installed in any position since prop shaft is balanced independently from other components. The only time one needs to mark anything on the shaft is when you're splitting the shaft for the purposes of replacing center bearing but that's something one rarely does, even audi considers shaft center support bearing a non-servicable item.

N_Jay

The front differential (not shown) uses synthetic gear oil.
The part in the center (#3) is the transmission and uses ZF spec ATF.
The rear part (#1 and maybe #2) is the center torsen differential and used synthetic gear oil.
I don't know where the seals are between the Transmission (#3) and the center differential, so I am not sure what fluid is inside of part #2.

I do know that the front, rear and center torsen do not use ATF.