A8CT

yes, there is a CV joint at each end of the shaft and a center support bearing in the middle.

I just replaced a diff seal on a '98, and the rear CV joint was dry as a bone. The grease was like hard paste.

I replaced my driveshft because I had a clunk in the front CV. Unless you know which of the three components it could be, I would probably go this route. You can replace the CV's independently but I don't think you can source the center support bearing.

KYNZ

In P its right around 1K but when i go to drive it drops to like 600rpm and idles really rough...vibrates you head on the headrest. do you think these two are related? maybe TC problem, since, once in D the TC is now under load? I only get my vibration (at speed) under acceleration, no other time.

sportQ

Someone with more experience should be able to confirm or deny this. But in my observations, I have a rough idle, large rpm drop when I change from N to D, and I have a shutter in the driveline that feels like the TC isn't operating like it should.

I just fixed my rear breather hoses and that helped the idle a bit. And, my idle solenoid appears to be in good condition. I plan on swapping the plugs here shortly, so I'll be able to rule that out.

Interesting note - a mechanic at a local dealership said the clunk we sometimes feel could be related to a dead or failing injector. I wonder if this is all related somehow.

ttuling

Presuming you have a gas V8...

I'd look for vacuum leaks, compare long term fuel trim values in VAG-COM with what range specified in the service manual, see what coolant temperature the ECM is reading, see if there are idle air control tests etc...

Because it does it in P, you have a simpler starting point. Hopefully there's only one problem behind it all.

Tom