I have a 2004 A6 2.7T Quattro. I have noticed that under light load in 6th gear, most notably going up a slight incline, I get a shudder. If I give it enough gas to make it change gears, it goes away but come right back if it upshifts. It happens sometimes on flat and level roads if I give it just the right amount of throttle. I have approx 85k miles on it and have recently had the 75k service which replaced the timing belt and changed the trans fluid. They said they found nothing wrong but I didn't request a look into the shudder at that time. There are no check engine light events either. I have an appnt for the 85k service/oil change and have this issue noted to check. It is under the Audi certified used car warranty. I am a bit worried as I have a trailer hitch on the car to pull a small utility trailer and don't want that to cause any voided warranty issues if it is a trans issue. BTW, it was doing this before the hitch was installed.

I have seen some post about similar issues and have been told it is possibly the plugs or coil pack. I doubt it is plugs as they were just changed. Possibly a coil pack? Would that always throw a code if that was an issue? Otherwise, it accelerates fine and has no other symptoms.

Thanks for any info.

 

The coil packs on the 2.7T only lasts around 100k. I had small shudders on my old S4 with 90k on the clock, which registered misfires in the ECM, but only threw a check engine light every 1,000 miles or so. If it is a random misfire, it will eventually throw a CEL, or it will be easilly found by the tech while driving. It could also be a cracked TBB (throttle body boot) the rubber pipe going into the throttle body. It tends to crack right at the split and leak boost. Cleaning the throttle body never hurts either.
Im just guessing here though, fault codes and data blocks would be needed to diagnose this.