How to find bad wheel bearing?

[Fred Munro]

----- Original Message -----
From: "Doyt W. Echelberger" <Doyt at buckeye-express.com>
To: "Eyvind Spangen" <eyvind.spangen at c2i.net>
Cc: <quattro at audifans.com>
Sent: Sunday, May 12, 2002 8:14 AM
Subject: Re: How to find bad wheel bearing?


<snip>

Stage two was performed on a lift that allowed the wheels to dangle,
unsupported. In this position, the car was started and put into gear and
allowed to run at a steady speed. Each wheel hub was examined in two ways:
The hub was touched and felt for vibration and compared to the other
wheels, and a stethoscope was applied to each hub and the grinding sounds
were compared. The fact that the bearings were not loaded by the full
weight of the car is a flaw in the above method. But we never found any way
to touch and listen with the 'scope without using the lift. And there is a
safety risk of getting tangled up in rotating shafts and wheels.

<snip>

Doyt, I've had good success using a contact microphone (the cheap kind you
can buy from Radio Shock to record phone conversations) attached to the
wheel hub. I hook it up to a portable recorder in the car and take the car
for a run. You have to do comparative testing - even a good bearing makes an
awful racket, so you have to find the noisiest bearing. This method also
works when hunting down tranny and diff noises.

Fred Munro
'94 S4