[s-cars] got a new sound
trgreen at comcast.net
Sun Mar 16 13:02:44 PDT 2008
Since you don't feel anything, I would suspect it is not driveline
Any small driveline vibration is usually easily felt in the seat of
I would look carefully at the heat shields for a loose piece that
in the airflow.
> Date: Sun, 16 Mar 2008 13:33:56 -0400
> From: Mike Fitton <rfitton at vt.edu>
> Subject: [s-cars] got a new sound
> To: s-car-list <s-car-list at audifans.com>
> Message-ID: <47DD5A04.7070002 at vt.edu>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 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
> 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
> 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
> with my prop shaft (no Krausky, not like sexually; or at least not
> 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
> 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
> 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?
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