[s-cars] got a new sound
jerryscott at wispertel.net
Sun Mar 16 17:44:16 PDT 2008
I have a file on prop shaft R&R from previous posts. Let me know if you
----- Original Message -----
From: "Mike Fitton" <rfitton at vt.edu>
To: "s-car-list" <s-car-list at audifans.com>
Sent: Sunday, March 16, 2008 11:33 AM
Subject: [s-cars] got a new sound
> 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?
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