Re: Funny sound

[steveb@falcon.kla.com (Steven Buchholz)]

> Paul said:
> -----
> I'm having a problem with an odd noise coming from the vehicle while its being
> driven.  The sound is similar to that of when you stick something in the
> spokes of a bicycle.  There's a constact ticking or tacking while the car is
> being driven.  As I increase the speed of the car, the ticks per revolution
> also increase. Drivability isn't affected, but my conern is that maybe over
> time the noise will lead to something catastrophic.  The car has 38,000 miles
> on it.
> -----
> Eric T. replied:
> 
> Speedo or its drive cable, perhaps? Although usually this will make
> your speedo act flaky, which I would think would be pretty obvious.
> 
The speedo is probably electronically actuated on the car, but I can state
this as a fact since I've never worked on a '94 90CSQs.  On my QTC I once 
had a noise that came from below the passenger compartment, and I found that
the parking brake cable was loose enough to touch the driveshaft.  I doubt 
that this is your problem, but it might be worth testing.  You can pull up
slightly on the brake handle and see if the noise goes away to test this.  

Other tests/possibilities ...

- drive at a particular speed in a circle with the steering at full left 
lock and then again at the same speed with full right lock.  Is the ticking
speed the same in both cases?  If so it is something at or before the rear
diff ... if it changes in speed it is at or after the rear diff.  You can 
tell which side to check based on the frequency of the noise ... check the
side that was outside of the turn when the clicking was the fastest.  

- U-joint in driveshaft?  if it is bad it might make such a clicking noise.

- ABS sensors contacting the sensor wheel?  I doubt this one because I'd bet
if this were rubbing it would make more of a humming sound ...

HTH!
Steve Buchholz
s_buchho@kla.com
San Jose, CA (USA)