A4 Auto Trans Acting Weird

Hi
It sounds a bit like the problem I was having last year with my 98 TDi, not exactly the same but similar.

I have the 4-speed auto and every time it changed gear the revs would hunt upwards before settling and when trying to hold at a constant speed (around 75-100kph) it would feel like it was going to change to 3rd then decide not too so revs would rise slightly then drop again with small surge in drive. Over 100kph it was fine and below 75 it would sit in 3rd without problem.

Turns out it was simply the trans fluid level. The auto box sump gasket was seeping and the level had dropped. I took the opportunity to drop the sump off, replace the filter and gasket and refill to correct level with fresh fluid. No idea how old the fluid was but it was pretty minging and the filter was fairly dirty as well. (271,000kms on the clock so may have been original). (Note that the 4-speed and 5-speed boxes have different filters)

Changing the fluid isn't too bad of a job, on mine there is a short pipe pointing upwards on the side of the sump pan which the new fluid goes into and I found it easiest to feed a hose from the engine bay into that pipe. However the level check has to be done underneath the car with the car sitting level and engine running and the gearbox fluid between 35 and 40 degC, I used VCDS lite to verify the last.

Technically not a difficult job but I found it lengthy and messy with lots of getting up and down and under the car. Simply topping of the fluid would be easier though and may be a simple thing for you to check first.

Quite a few videos on youtube with people doing it which was a great help.

Stuart