View Full Version : Vibrations & oscillations

10-25-2012, 04:25 AM
Recently started DD'ing my '98 A4 2.8QM, I've got roughly 500 miles under my belt (back story here: http://www.audizine.com/forum/showthread.php/504394-Fixer-upper?p=7988303&viewfull=1#post7988303)

I've got two annoyances that I'm trying to squelch.

A) Oscillation in the steering wheel. This one I'm not too worried about. I figure it's due to either a worn joint, imperfect alignment, out of balance wheel, or a worn axle.

And the one I want to get rid of first

B) Slight vibration in the whole car, while accelerating, decelerating, coasting, though it is not noticeable all the time. This is most evident between 50-55mph. However I think it is related to another noise/feeling: 50% of the time, while accelerating hard in 2nd, there is a rapping or tapping in the floor just behind the front seats, which I imagine is from the driveshaft. The rapping/tapping in 2nd is slower in frequency than the high-speed vibration (i.e. I think the vibration is speed related). At high-speed, I estimate about 5-10 pulses/second. I really think something is the driveshaft is amiss. What is a common failure in this part? Guibo, U-joint, support bearing? Are the u-joints serviceable?