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E30M42cab
10-10-2009, 07:12 PM
Could someone please explain to me the different sounds each of the following make when they fail:

1) Differential

2) Half Shafts / CV joints

3) Rear Wheel Bearings

My symptoms started off as a whining when I feather the trottle to match the revs of the wheels (not while the trottle is on, but not letting the engine slow the wheels down either). Then it went to a ticking just as I would come to a stop. Now it's a grinding/clunking all the time. All the clunks are directly related to the wheel spinning. Seems to be worse on the driver's side. I changed the diff fluid a few months ago, and that had no effect. The car is lowered, and has an open 4.27 diff.

Thanks!

e30_kid89
10-10-2009, 07:38 PM
You mentioned ticking/grinding = Half shafts.

ACS_DAN
10-10-2009, 07:57 PM
1)Differential will be more of a whine. offtopic but, in some countries they put banana peals in there before they sell a car to quite down a differential.


3)Will be more of a hum/vibration noise.

E30M42cab
10-10-2009, 10:57 PM
I had a rear wheel bearing crap out on my E34, and the wheel was actually wobbly to pull back and forth on it. I jacked it up tonight, and my wheels are firm to pull back and forth on. I spun the wheels and the drivers side clunks and grinds, but seems like it's coming from the wheel end of the half shaft, not the diff. Also, just for fun, both rear shock mounts are shot. I'm using E46 cabrio mounts with Z3 reinforcment plates and koni adjustable shocks... apparently not a winning combination. Only lasted a couple years.

Dissembler
10-10-2009, 11:20 PM
You mentioned ticking/grinding = Half shafts.

+1, easiest way to diagnose a bad shaft if too put the wheel full lock in one direction, going slowly in circles (about 15-20kph) jab the throttle (your not trying to do burnouts though) if the clunk corresponds to jabbing the throttle, listen to which side is loudest. Wheels turned left = right side shaft, wheels turned right = left side shaft.

This method works guaranteed for FWD vehicles, never really tested on RWD to be honest, but the principal still applies: turning the wheels stresses one side of the car, jabbing the throttle causes any freeplay in the shaft's CVs to make itself apparent

could also be your parking brake, check to make sure its not stuck in the "engaged" position, shoes could be "walking" back and forth inside the drum part of the disc.