Thread: Rear End Howl
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Wolf300tt Wolf300tt is offline
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Join Date: Sep 2005
Location: Erie, PA. Cape Coral , Fl.
Posts: 649
I think that the release bearing will show itself to be bad at any RPM and any speed. If you apply any pressure on the bearing at all and the noise goes away, then the bearing is potentially bad. On the other hand, if the release bearing is totally shot, it will grind when pressure is applied.

I don't believe the wheel bearing is the culprit. You seem to have eliminated that with your on-throttle off-throttle test. Most of the load on the wheel bearing at cruising speed is from gravity, and the weight of the car, not the torque of the engine. Since the noise goes away by disengaging the clutch, I would say that the problem will be found elsewhere.

My guess (albiet amateur) is that the problem lies between the mechanisms you are affecting when you engage and disengage the clutch: clutch disc, flywheel, and input shaft of the tranny.

I think you have all but eliminated the flywheel because you said the noise doesn't show itself when you free rev. A loose flywheel will vibrate while free revving, and will quit vibrating when you hold in on the clutch because you are effectively pushing the flywheel into place with your foot. A bent or out of balance flywheel will always vibrate at a certain RPM regardless of whether the clutch is engaged or not.

The clutch disc itself doesn't seem to be it either. The disc is clamped in place while cruising, and is somewhat free spinning when disengaged. When clamped in place, it is part of the flywheel (so-to-speak), and can't make noise on it's own.

That leads me to suspect an internal tranny problem.

Once again, I am a rank amateur, and believe me there are far more senarios that could explain your dillemma. I only hope I am wrong, and that the real experts chime in and shoot big holes in my theories.

Good luck with it!

Old 01-09-2008, 07:02 AM
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