Driveline vibration help - '84 4KQ

[Doyt W. Echelberger]

On big US V-8's, a bad motor mount will allow the engine to lift visibly 
when you blip the throttle from idle. They can jump several inches. Might 
apply to Audi's.

Open the hood in good light. Have someone blip the throttle while you stand 
at the SIDE of the car and watch the engine movement. Don't get run over by 
standing in front of the car.

As mentioned above, this test works well on big US V8's. The engine may 
rise 2-3 inches and drop back down with a resounding thump. They will even 
rap the underside of the hood when tested with the hood closed.  I never 
tried it on an in-line 5 Audi with bad mounts.   I've had two I-5's but 
they have good mounts. However, the theory is valid, and may be revealing.

The above advice is only a partial answer. If your car has original mounts, 
the ones that get the most heat and oil contamination will probably need 
replacement and have probably been failing for several years. If you are 
guessing, pick the ones most likely.

I swapped mine when I changed engines in the 86 4kq. They were bad, 
consistent with the degree that they had been abused by heat, oil, and age.

Doyt Echelberger


 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
At 06:27 AM 1/17/2002 -0500, you wrote:
>Hi all,
>
>I hope someone out there has a good method for diagnosing a bad motor 
>mount or transmission mount.  I get a pronounced vibration all throughout 
>the car especially in 5th gear at highway speed (65mph and up).  When I 
>put the clutch in at speed, the vibration goes away.  This is why I 
>believe it to be a motor/transmission mount problem.  Also, in 1st or 2nd 
>gear, when I let off the throttle at 3K-4K rpm while still in gear, I get 
>an occasional clunk.
>
>Thanks in advance.
>Carl