I've been reading and searching till my eyes are ready to fall out and I'm not finding any other posts talking about this sort of problem.

I have a 2000 A6 avant quattro, 2.8 engine, with 250k on the clock. I have a very minor tranny fluid leak at one of the transaxles that's been there since about 100k. I top off the tranny fluid once a year and it usually takes between .25 and .5 quart to top off. In ’06 and in ’09 I did a full fluid and filter change. The tranny has always been very solid when shifting and has worked flawlessly.

This week when accelerating lightly around a corner, it thumped hard going into a gear. All week, it’s consistently getting worse and more frequent. After driving it around and experimenting with accelerating, corners and shifting, I’ve nailed down when it does this. When it goes from 2nd to 3rd, it shifts in fine, car starts to accelerate, then it comes out of gear for a second. It revs as if in neutral, then slams back into 3rd and stays there until it shifts into 4th. 3rd gear is the only one it does this with.

There are no error codes associated with this and it doesn’t go into limp mode after it happens. It still continues to drive normal and shifts through the rest of the gears fine.

The day after it did this the first time, I left it parked so I could top off the fluid that night. It was less than 1 cup low. I don’t really want to do a full fluid change since I just did it last fall and the fluid still looks decent. Not clear, but definitely not as muddy as others I’ve seen.

I’m stumped on this one and am almost ready to give up and take it in to the dealer for diagnosis. Any ideas or thoughts before I do that would be greatly appreciated.

 

There is no such thing as "full" fluid change.
Your statement makes me suspicious on the way you have dealt with the atf!
What was the atf you used?
How do you measure the level?
What is the fluid color?

 

Sorry, I was out of town for the weekend and just got back online.

By "full fluid change" I meant that I dropped the pan, & changed the filter, leaving the whole thing drip for the night. I understand that doesn't remove all of the fluid.

Fluid is Pentosin ATF from Blau parts.

Fill process is basically: with the car level and on blocks, start car from ambeient temp, wife goes through all of the gears twice for 30 secs per gear, while I pump atf into the fill plug on the bottom of the pan. keep pumping until she's gone through the gears twice, then cap the fill plug and drive.

Color of new fluid is almost see through very light brown.

Additional symptom started on Friday while driving to the airport. Now it does the same thing in both 3rd and 4th. I have more fluid and filter ordered and based on other posts I found on the Bentley site, I will try another change before I take it anywhere to look at it.

Thanks
Paul

 

The procedure looks like the proper one.

An you pump the atf in till (on P) it starts overflowing?

I'd suggest a new oil change would be a money waste.

Perhaps this is the end of transmission life - the color of the atf and the lack of debris
could point to valve body issue.
Call ZF and discuss the issue with them - there are occasions people were suprised by the help they received.

 

Thanks nemohm.

My dilemma was that I really didn't want to put another 150 into fluids and filter if there is something in it that is shot and causing this regardless of whether it has fresh fluid or 9 month old fluid with 15k on it.

Maybe I misunderstood your question about the fluid color. The color of the current stuff in there is a bit dark. Not nasty blackish like some I've changed, but not like new either. I thought you were asking what color was the new fluid I was putting in.

I guess I never even considered I'd get any sort of direction from ZF. I'll look them up and give them a call.

Would a bad valve body affect all gear shifts or would it go bad one gear at a time? All gears still shift smooth and solid except 3 & 4.

Also, I figured out after leaving the airport last night that when cold, there were no problems shifting into 3 & 4. After it got warmed up on my 25 minute ride home, shifting into 3 & 4 were a problem again. Basically the opposite effect of when one is low on fluid.

 

Something to look into:

http://www.eurodrivers.ca/forums/showthread.php?t=19795

 

Holy crapolla! I assume that was meant to scare me into just replacing the whole thing and being done with it!? ;o)

So based on that and some other reading I did yesterday, each gear has it's own independent control function inside of the valve body and each one can behave differently based on what's happening in there. That all gives me a sinking feeling about my trans.