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Hello all, this is my first official post to this forum, and I am excited to hear from others that have the same interests in autos as I have.

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I have recently become the owner of a 2000 A6 that I consider to be be in fairly good shape. I have come across a vibration that I am unable to diagnose. I have recently replaced the drive shaft assembly, the entire front control arm suspension, both tie-rod ends, and the wheel bearings. Most of these parts were at their limits when I received the vehicle, but now that all these other noises, and clunks are out of the way, my vibration, as described in the title, persists. I ordered cv's, I thought it fair to install them before I become really serious about this dern vibration. Its more of a shudder really.

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Another issue that leads me to the cv resolution is that as the suspension cycles, the length of the cv will either elongate, or retract. By doing this, the axle will have the opportunity to ride without inhibition and ride on its worn tract, or be pulled out of its worn nature, into a "out of round, vibration" position. The key to this, is that at normal terrain, being flat, and without enough hill to cycle the suspension, the ride is as smooth as can be. The vibration comes only when I decelerate at above 60+, or the terrain cycles the suspension from ups and downs on the highway.

SloopJohnB@mac.com

Don't discount the driveshat in addition to the axles. It's balanced as an assembly but it could be a center bearing.

Prospeeder

I see the vibration on acceleration when the inner joints wear out on the axles. Get the car on jack stands and rotate the wheels by hand and watch the inner joints. if they See to wobble or have any play there junk. This is why I never just reboot the original axles like some people here all insist on because the axle as a whole fails quite often. Replace the axles with some reman or new axles.

old96A4

Does is feel like a tire out of balance?? check to make sure your alignment is good, the car is going down the road straight. my car was jumping down the road at high speed. I couldn't figure what was wrong and I had to move both tie rods to the right to straight the alignment and it fixed it. just make sure the steering wheel is straight when the car is going down the road.
I know that sounds dumb, but until I got mine straight the tires would jump and the tire would wear fast. also had issue with camber in the back tires. car was a mess, once I got the tires straighten out goes pretty good now. I have yet to find any one that can align these cars right...

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I installed a new drive shaft assembly, and as far as the wheel balance, I replaced the whole set, new wheels and tires. The car tracks well, but an alignment is definitely in order after I install the cv's. I have replaced so much on the front end, It's going to need it. The symptoms have not changed a bit. Still the shudder/vibration on decel, and when I'm at speed, it does it when I go over dips in the highway. Not bumps, but dips. I sure hope new cv's do the trick. It's a little unnerving that I have not seen this issue on any threads, on any websites.

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I installed a new drive shaft assembly, and as far as the wheel balance, I replaced the whole set with new wheels and tires. The car tracks well, but an alignment is definitely in order after I install the cv's. I have replaced so much on the front end, It's going to need it. The symptoms have not changed a bit, not even a little. Still the shudder/vibration on decel, and when I'm at speed, it does it when I go over dips in the highway. Not bumps, but dips. I sure hope new cv's do the trick. It's a little unnerving that I have not seen this issue on any threads, or other web forums.

Huskerbob

You replaced the center drive shaft?

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Yeah, the entire assembly, as one balanced unit. Did not even phase the vibration. Whatever it is, it's a rotating component, and it happens as the suspension cycles.