Hello,

I have a 2005 A6 4.2 that I've been having a hard time with. This spring the Torque converter went out, had that replaced, it was confirmed bad by ZF, a seal had broken inside. After this for a while it had a weird vibration accompanied by a surge. The shop recently replaced the Mechatronics unit, and the vibration doesnt seem to be there anymore. They said the transmission fluid was never discolored or smelly, so they doubt there was clutch damage. I am on the newest software version for the HLL transmission (80) and have the newest fluid in the car, i think its green now (newer then the blue).

Now, when i am driving 60 - 70 MPH, the engine RPM will vary up and down about 50-100 RPMs. The confusing part that it will NEVER do it with the cruise on. When its cold out i notice a slight surging also, particurlary noticable when going uphill; no vibrations though that i notice; again doesnt do it with cruise on. Even accelerating with the cruise + button will not cause surging; also if you set the cruise at a lower speed and use the gas pedal to go faster it will surge again. Then sometimes it doesnt do it at all, even with cruise on.

So, if it was a clutch pack, wouldnt it persist even if the cruise is on? Or is the transmission aware that i have the cruise on and changing how it is using its clutches? Im confused here, but i already paid about 4k to have all this done, dont really want to throw down another 7k to rebuild the tranny.. I do have a VCDS and a VAG cable.

Any suggestions? Is it something i should just get used to? I've heard some of the ZF 6 speeds are just weird in some ways, but i dont remember it happening before the torque converter went.

I do know that one of my tires is 1/32" larger then the others, it is currently on the front; one had damage within 3000 miles of getting new tires; about the same time the TQ converter went out.

Thanks!

 

Have you looked into the throttle body being the problem?

 

You think it could be the throttle body? I would think it would still happen with the cruise on if it were that.

Wonder if it has something to do with the fly by wire throttle being too sensitive maybe? I have looked around a bit but haven't been able to find anything about that. Kind of a weird coincidence if it is something else with all the other transmission issues..

Thanks