testarossaguy

My 01 A8L has a slight vibration between 45 and 55. Below or above this range and everything seems great. It is not a wheel/tire issue as the vibration frequency is higher by a factor of 2 or 3 based on my "seat of the pants" meter. I recently added a set of new RS4 wheels and tires and this problem existed prior to and now after the chang. I'm guessing it may be a drive shaft issue. The vibration sounds like a deep base flutter...sorry for the crude descriptions. My car now has 104k miles on it. Any ideas on where to look for the source of this vibration? Thank You Gang...

KYNZ

I have replaced both tranny mounts, both rear hydrostatic (is that the correct name for them) motor mounts, replaced the Driveshaft, new plugs, spark control modules, high speed balanced all wheels/tires and i still cant seem to shake this little 2000 rpm vibration at higher speeds (40, 65, 72mph in 3, 4, 5th gear respecitvely). Ive checked my Coil packs as maybe they are arching but i do not throw ANY codes, misfires or otherwise (since i replaced my SCM or Power Output Stages) This is obviously not a design flaw in the A8 as everyone dosent have it so what could it be? a Wheel Bearing would squeal and vibrate all the time, control arms - again, vibrate all the time and at a more obvious sensation in the steering wheel. Could it be a Torque Converter issue with the tranny? I know this has been an ongoing issue and if anyone could enlighten us as to a solution that would be great.

MikeTTR225

it could be the wheel hub starting to oscillate on a wheel bearing that is just starting going bad, it can be seen on a lift with the wheels going by looking thru the center of the rim. Thats how i saw mine looking from the inside out.

sportQ

I can feel two distinct vibrations in my A8. The first I think is TC related and feels like the engine is in a gear too high for the situation. The second is a slight shimmy that is felt at the wheel at a specific speed.

I don't know about how to resolve the first issue, but the second MAY be either related to the steering rack (servotronic) or overtightened\warped brake rotors, or a combination of both. I'm inclined to think this way because I feel the same sensation in my allroad. Now, I had the vibration bad before I took my car in for the suspension. After I got it back, it was greatly diminished. I may have slightly overtightened the wheels the last time I put them on, which further reinforces my thought on this. Add to this that someone else on here resolved their vibration issue by swapping out his rotors and things start to come together just a bit.

crazy-8

Is the vibration in the steering wheel or in the seat? If in seats, is it more prevalent in the drivers or passenger side?

Is the vibration present with and without pressing the accelerator pedal? Try coasting in Neutral on the highway

Is the car pulling to one side or tracking straight?

If it is vibrating with acceleration I would focus on ignition and drive-train type issues.


If it is while coasting, I would stick to mechanical issues surrounding the wheels, brakes, shocks, struts, bearings etc...and make my way to more complicated and expensive systems.

I have a similar issue with my 98 A8Q ~110k miles. Mine occurs at 60 mph and up. With or without acceleration and is in the seat. Car tracks straight at all speeds. Steering wheel is like a rock. car feels like there is drag or resistance on the highway.

My plan of action is to check the following:
1. Balance tires (done no improvement)
2. Alignment (getting 4 new tires this week anyway)
3. Rim condition
4. Wheel bearings (see other posts, a8 bearings can have a different failure symptom than the classic)
5. Brake rotors and calipers
6. Shocks and struts
7. Rear control arms
8. drive-train and tranny (hope i don't have to go here!)

I'll let you know what I find.
-B

A8CT

in the drivetrain. When you put the car in neutral, the propshaft is not disconnected and continues to spin.

You can do this to isolate a specific RPM issue though.

Bob

testarossaguy

The vibration in my car is independant of the wheels and tires I think. In neutral while coasting, rev engine, no change in vibration. Is there a bearing at either end of the driveshaft that could be worn? As others have said, I feel it in the seat and the body of the car, not the steering wheel. The car drives great other than this annoyance. My last high mileage 1999 A8 had this same problem as I recall.

Landjet

Yes it could one of the bearing/ujoints on the driveshaft. Mine started the vibration at around that speed and got worse until it was vibrating at even lower speeds. A good mechanic in Montreal had a connection to get the rear bearing cage fixed instead of replacing the whole driveshaft $$.

sportQ

BTW, is your idle rough? When you go from N to D, so you see a large rpm change? Just curious to see if you have similar issues to mine. Someone a lot more experienced may be able to connect the dots.

jwalther

my vibration, felt through the seat, not the steering wheel, is intermittent. I feel it sometimes at low speed, driving around town, and most of the time on the highway. My issue is not related to engine speed, as I can downshift from d-4 at speed with no change in the intensity or frequency of the vibration. I don't hear any noise at all, which leads me to think it's not a wheel bearing problem. I also have the typical hunting/thumping/tc issues, so maybe it's tranny related. My tires are due to be rotated soon, so I guess I'll have the shop check the bearings and tires for balance, and definitively eliminate those two causes.

Jeff