[s-cars] got a new sound

[chris chambers]

Mike,

if it increases with ground speed and not RPM I wouldn't look at the
trans.

I had a strange noise that increased with ground speed and it
ended up being the LF caliper had "lost" of of the retainin bolts
which allowed the caliper to pivot partly out of the carrier.

I'd start with axles, prop shaft, wheel bearings and I would
check the brake pads for drag.

HTH
Chris







--- Mike Fitton <rfitton at vt.edu> wrote:

> And I'm at a total loss.  It's a very clean vibration.  Don't feel
> it, 
> only hear it.  Frequency rises with ground speed.  Amplitude varies. 
> I 
> don't hear it below about 20mph and not above about 65mph.  It's
> loudest 
> around 50-55mph.
> 
> I've ruled out everything engine by turning the engine off at 55mph
> in 
> neutral.  Stick and clutch position don't change anything.  Steering 
> wheel doesn't change anything.  Wheel bearings all pass the 
> autocrosser's tech inspection test.  All CV boots are tear-free as
> far 
> as I can tell, and none of the usual grease sling that comes with
> torn 
> boots.  No perceptible alignment changes.  No corollary bugs at all
> that 
> I've noticed.
> 
> About two months ago, I changed out my transmission oil (finally).  
> Amsoil's synthetic 75W90 GL4.  All the plugs are still tight and the 
> stick still feels great.  The sound started very suddenly about a
> week 
> ago, so I'm guessing it's not that.
> 
> Two weeks ago (one week before the sound started) I switched back to
> my 
> summer tires.  Drove on those just fine for the first week. 
> Pressures 
> are consistent.  Verified lug torque at 90 lb-ft for all 20.  Rotated
> 
> them anyway with no change.  Tires and wheels all look fine, and no 
> feeling of imbalance in the drivetrain.
> 
> All I can think of is the prop shaft center bearing.  I've never 
> experienced that before, so I don't know how it should sound.  I
> played 
> with my prop shaft (no Krausky, not like sexually; or at least not
> right 
> then) and found a little front to back play which seems like it would
> be 
> normal with a CV joint on either side.  The two halves seem to move 
> equally during this exercise.  There's also a little play
> perpendicular 
> to the shaft at the center - that is, I can bend it
> up/down/left/right a 
> little at the center U joint.  I never did that before, so I don't
> know 
> what's normal there.  But it seems to me like it shouldn't do that,
> so 
> that's my best guess so far.
> 
> But before I give up on diagnosis and resort to just throwing parts
> at 
> it, I want some second opinions.  Anyone?  Bueller?
> 
> -Cheers!
> Mike
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