4KQ, Suspesion Vibration & Clunk

[DGenetti@aol.com]

 Car: 1987 4000 CS Quattro with over 100K mi.

Possible Problem Areas: Suspension, Steering, Brakes

Indications:  
*  Vibration felt through steering wheel at freeway speeds, 
     not severe but annoying.
*  Clunk noise when straightening wheel after backing out 
    of a parking space.
*  Clunk noise when hitting bumps, speed bumps and driveway 
    entrances.
*  Some oscillation under hard braking with a clunk in the last 
    couple of feet before coming to a complete stop.
*  Tow angle feels OK, the car does not pull to one side on the 
    freeway.

Items checked so far:
The vibration started with an old set of tires.  I replaced them 
with a new set of Goodyear’s and had the alignment adjusted. 
Since then I have had the new tires re-balanced and rotated.

I found some radial play in the steering rack of about 2 to 3 
degrees and couldn’t feel any looseness in the ball joints or 
tie-rod ends.  Not knowing how much play is acceptable
in the rack, I had a “reputable” Audi shop look at it.  They 
said that everything was tight and that the control arm bushing 
where OK.  They didn’t feel much on the test drive.  I was not 
overly impressed with their evaluation; they failed to inspect the 
brake rotors as requested.

Work done in this area in the past includes new outer CV joint 
on the left, new rotors and non-metallic pads, H&R springs, 
Boge T-gas cartridges, and new strut bearings all about two to 
three years ago.  Brake pressure proportioning valve was 
replaced about a year ago.

Questions:
*  Is the play in the rack normal, how much is acceptable?
*  Could warped rotors cause vibration at freeway speeds?
*  Is it possible that there are two problems here?
*  If a new set of rotors warps quickly are there other brake 
    parts that may need replacing?
*  Are there other components that I should be looking at?

Thanks in advance for your input,
Damon