Was driving my 03 A6 2.7T home last night was some (very little) snow on the freeway cruising (cruise control) at 70mph....all of a sudden it felt like the transmission was slamming in and out of gear. It happened about five times on a 30mile trip. Wasn't totally violent but almost like getting rearended at 3-4mph. Had vehicle on cruise control...when it happened it only happened for a second. Got home and had to run out back about 15miles hopped on freeway all the same scenario and had no issue....same thing this morning no issue again. What the heck happened. It is quattro w/ 77k miles. I know this may sound weird but I had a 98 lumina that did Almost the same exact thing for a couple days took it to chevy and the Crank Sensor was bad and throwing a weird signal to ecm causing it to buck (as they called it) but thats exactly what it felt like/and feels like on my A6. Any Ideas!!!

 

Have to pull the codes - if any!
Have you ever changed the fluid?

Slamming events happened rarely with mine - never codes.
Happens with other cars I know - A8, S8.

I tend to believe this could be based on electronics malfunction, or the fluid is out of specs (worn down) and the TM has hard times to match the programs.

What happens if you drive on sport mode or manual?

 

Not sure like I said it only did it that one trip, did not happen again...no check engine light or anything. I would think with as violent as it was if it was a voltage/communication issue with the TCM or ECM it would defineitly throw a check engine light....as for the fluid I read that its a fluid for life in that Trans....am I wrong?

 

Another reason I prefer MT6 - more predictable. I'm wondering if your ESP was kicking in due to tire slippage? Did any icons go on in the dash?

If it was engine missing you should show CEL and codes. If it was the transmission, not sure if any codes would be thrown. Let us know what you find out.

 

Cruise control on a slippery road ---- most likely tire slippage like ppgoal sugested...

 

That's exactly what the dealer shops want you to believe. Almost any car needs a transmission flush at least every 50,000 miles.
The better you care for the transmission, the better it will serve you without any capital (and very expensive) repairs.

 

Damn -- I must be in trouble with over 200K miles on my A6 Avant and an auto trans with out a fluid change.

I would suggest you read about the problems people have had when they attempted to flush their Audi transmissions before making any decisions.