8 3/4 rear clunk when brakes are applied

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gormbj35

72 demon
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buffalo ny
i am new to this site but think it can help.
i have a 72 demon 340 4 speed 8 3/4 rear with 4.56 posi. i have had the car for 6 years a month ago i noticed that when the car was moving and when i first hit the brakes i hear a loud clunk coming from the rear of the car. i have gone under and found nothing but when the car is in nuturel their is some play. also when i turn one of the rear wheels one way by hand then the oppsite direction i hear a simmilar clunk. i dont believe it is the brakes. i alos put in a new hevy duty driveshaft and u joints 2 years ago. this noise occurs when the car is moving fast or verry slow and i hit the brakes but if the car is not moving at all and i hit the brakes nothing. the centercection was replaced 7 years ago but was used and i dont know nothing about it. i think my problem is the rear but i am not sure, also if it is the rear could it be the axles? they are problly realy old but i am not sure, would it be the centercection? i dont have any m oney so i cant take it to a shop i do all my work myself but troubleshooting can be a problem for me any ideas or help would appricieated thanks
 
I had a similar..clunk..in my 8 3/4 s.g rear last year.Turns out it was the cone style sure-grip was kaput.I purchased a used centersection and had my 4.10 gears installed in it,then installed the center myself.Works fine now.That,s what my clunk was,yours could be different.My 2 cents.I,d start searching for a new center,they run anywhere from $400-$600.but there is still some cheaper in these tough times.Good Luck!

P.S Welcome to the best A-bodies site on the Planet!
 
Sounds like slop in ring and pinion. normally more noticeable with an automatic, going from park to r or d, not necessarily from brakeing? You might want to pull drums, see if any brake hardware has come loose. the adjusters may not be working properly, giving a lot of play, and when you hit the brakes, bam. update us on resolve:happy10:
 
i am going to check drums out on monday thanks for the replys i will put a new reply mon or tues
 
Maybe you can duplicate the sound with it running, on jack stands. Get somebody in the drivers seat, while you listen underneath, w/ a "broom stick" stethoscope", if necessary.
 
pagilman said:
If your lucky its a u-joint
Click to expand...

First place I'd look too. Easy fix if that turns out to be the problem and you get it fixed before you blow out a U joint completely and take out the driveline or something else along with it.
 
I'd say it's the center piece of the rear axle. Quite common up here in sweden since it's not uncommon that some 18year old put 300 horse on a stock volvo rear axle =D

No but seriously, that's my guess. Had the same prob in my '67 142 and it broke quite soon after the noises started coming, shot the whole axle center.

My advise is change it, nothing lasts forever
 
Remove you driveshaft and check your pinion nut, I have seen these back off a bit and left unchecked could be dissasterous to the 3rd member....
 
I ran across one doing that once and it was loose bolts holding on the backing plates. Tightened up the bolts and it was fine. Luckily it wasn't driven long that way or they would have been wallered out. Something else easy for you to check.
 
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