Re: 4KQ, Suspesion Vibration & Clunk

[Huw Powell <human@nh.ultranet.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.

> 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. 

OK.  My rack had a few degrees of play a few months ago.  I have
replaced the struts, strut bearings, and all 12 front end bushings (not
like yours though) and competely rebuilt the rear axle assembly
likewise.  brakes all new.  Car just was not tightly aimed and exhibited
a clunk like yours, though the front and rear end work both made it less
obvious.  the rack play got a little worse.  My "easy" parts car - the
one without an engine in the way - also had a little play.  Queried Q
list - owners report "no play" is the normal situation.

Pulled the parts rack, sent it to Jorgen with about $170, got back
rebuilt rack.  Put it in.

I'm not certain if the clunk is gone, since it didn't occur much
recently, but the steering is *totally changed*.  there is no doubt
about the relationship between the steering wheel and the road now.  the
car doesn't skitter L/R when taking off with poor traction (remember I'm
2wd) anymore.

I would seriously look into replacing that rack if I were you.  jorgen
does a core charge system.  You'll need new fluid (they told me to use
7.1... who knows?), two liters - one to waste getting the old fluid out,
one to fill it up, and a new filter (about $20 @ dealer).

Also I would consider the condition of your subframe, control arm, and
sway bar bushings; strut bearings and hub bearings.

It's really frustrating putting new parts on until all the old worn crap
is replaced - you don't get the benefit you should til then.

if you want to know more about the rack swap ask me.

> said that everything was tight and that the control arm bushing
> where OK. 

What is "ok"?  passes safety inspection or as good as new?

> They didn’t feel much on the test drive.

they wouldn't.  nobody but a fanatic would have noticed anything wrong
with my car.  But a little looseness in the front end of an Audi is a
probelm, they are supposed to be dead nuts tight and true.

> Questions:
> *  Is the play in the rack normal, how much is acceptable?

No & none.

> *  Could warped rotors cause vibration at freeway speeds?

only while braking

> *  Is it possible that there are two problems here?

yes, see above.  But it sounds like most of the possible culprits have
been replaced.  Your bushings are suspected accomplices to the rack
problem to me.  Do both.

hope this rambling response helps

-- 
Huw Powell

http://www.thebook.com/human-speakers

82 Audi Coupe; 85 Coupe GT
http://www.nh.ultranet.com/~human