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From: clewis@mnetor.UUCP (Chris Lewis)
Newsgroups: net.auto
Subject: Re: GM BRAKING PROBLEMS
Message-ID: <2020@mnetor.UUCP>
Date: Thu, 5-Sep-85 14:27:52 EDT
Article-I.D.: mnetor.2020
Posted: Thu Sep  5 14:27:52 1985
Date-Received: Thu, 5-Sep-85 15:16:16 EDT
References: <2688@ihuxf.UUCP>
Reply-To: clewis@mnetor.UUCP (Chris Lewis)
Distribution: net
Organization: Computer X (CANADA) Ltd., Toronto, Ontario, Canada
Lines: 35
Summary: 

In article <2688@ihuxf.UUCP> churm@ihuxf.UUCP (b.r. churm) writes:
>
>Currently there are two cars involved. Both 1982 GM A-frame issues.
>One is a Buick Century the other a Pontiac 6000. Both have about
>30K miles on them, give or take a few thousand. 
>
>The problem is intermittent and occurs while braking. It occurs
>under all types of braking conditions. What happens is that
>when the brakes are applied a thunk, thunk sound occurs from the
>back of the car. It sounds somewhat like the sound you have when you 
>get a flat tire.

Are you sure it's the back?  Sometimes the noises can be misleading.
Have you got disk brakes on the back?

Did you check the front brakes too?  We had a similar problem on
an X-body, and it turned out that the surface of both rotors of
the disk brakes were breaking up.  The thunks were teeth-rattling.
On a rear-wheel car I have, I was getting substantial klunking from
a combination of thin rotors (possibly warped) and partially seized
pistons.

Another thing I can suggest is that maybe something is wrong with the 
rear axle/bearing assembly.  I once had a similar problem on a rear-wheel
car, but the noise was more of a cruuuuunch-cruuunnch which we originally 
thought was brake or differential problems - but, the axle bearings were 
shot.  (you might be able to tell by raising a rear wheel off the ground
and trying to see if the wheel will move with the suspension staying
still - particularly side-to-side slop instead of vertical)

Are the thunks related to tire speed or engine loading?
-- 
Chris Lewis,
UUCP: {allegra, linus, ihnp4}!utzoo!mnetor!clewis
BELL: (416)-475-8980 ext. 321