Clunking from rear end after stopping
Thread Starter
8th Gear
Joined: Apr 2002
Posts: 8
Likes: 0
From: Arvada CO
Clunking from rear end after stopping
My 79' is an automatic and for some reason, after its good and warm, develops a clunking vibration coming off of a stop. If it is an excellerated start, the vibration and clunking is minimal, however if the car is alowed to move forward by only releaseing the break, the clunking is severe and doesn't go away until excellerated. Has anyone had this problem and/or found the reason?
Drifting
Joined: Sep 1999
Posts: 1,439
Likes: 1
From: Hagerstown MD
Re: Clunking from rear end after stopping (Rino)
There is a stamped steel bracket mounted at the front of the differential. The cushions are mounted between this bracket and the frame. I don't know much about replacing them, apart from the fact that I'm going to replace mine when I put the drivetrain back in my car.
Melting Slicks
Joined: Nov 2000
Posts: 2,663
Likes: 3
From: Palm Harbor FL
Re: Clunking from rear end after stopping (Rino)
Is it a single clunk, or a repeating clunk? The single clunk on start up or deceleration would sound like a front differential mount cushion. However, a repeated clunking on acceleration sounds more like universal joints.
Thread Starter
8th Gear
Joined: Apr 2002
Posts: 8
Likes: 0
From: Arvada CO
Re: Clunking from rear end after stopping (79MakoL82)
It's a continual clunk clunk clunk untill I pressure it up by accelerating. Does it make sence for a u-joint to only do this after you've driven it for awhile?
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
Re: Clunking from rear end after stopping (Rino)
Been there, done that. If it does it when you are moving perfectly straight, it is a good indication of the u-joints. If it does it when the front wheels are turned, it is in the differential. The differential fluid requires a posi-traction additive. You have to purchase the additive separately and put it in the differential case. You can purchase this at GM or through a parts store such as Napa or Carquest. After awhile that additive breaks down and has to be replenished. What happens is that when this additive breaks down, the gears do not mesh as easily (they lose their limited slip). When I ignored it the first time, I broke a bolt in the differential case. Fortunately, it did not damage anything else and I just had to replace the bolts and put it back together.
Melting Slicks
Joined: Nov 2000
Posts: 2,663
Likes: 3
From: Palm Harbor FL
Re: Clunking from rear end after stopping (Rino)
It's a continual clunk clunk clunk untill I pressure it up by accelerating. Does it make sence for a u-joint to only do this after you've driven it for awhile?
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Michael S. Palmer
Race Director
Joined: Dec 2000
Posts: 10,896
Likes: 2
From: CO
Re: Clunking from rear end after stopping (79MakoL82)
This is similar to what happened in mine.
I would drive it when cold and it would not make the sound. Then after driving for an hour or so , when I stopped it would make a clunking sound. What mine turned out to be was a worn diff. the yolks were rubbing on the case of the diff. Might want to visually check your rear end and see if there are any signs of wear.
I would drive it when cold and it would not make the sound. Then after driving for an hour or so , when I stopped it would make a clunking sound. What mine turned out to be was a worn diff. the yolks were rubbing on the case of the diff. Might want to visually check your rear end and see if there are any signs of wear.
Burning Brakes
Joined: Oct 2000
Posts: 936
Likes: 0
From: Chicago Illinois
Re: Clunking from rear end after stopping (Rino)
A bad U Joint can clunk on decelleration and accelleration, basically you figure the torque of the drive shaft is being produce by the motor on accelleration. When you step off the gas or decellerate, now the torque is being produced by the wheels, so the motor is being turned by the drive line, instead of turning it - change of direction, then U-joint may clunk any time the torque transfers direction. Not sure how clear the explanation is, but it's easy and takes a minute to check the U joints. Just reach under the car and firmly grab the drive shaft (and half shafts) and give them a real good firm twist & shake and check for any free play. And if you do need new U Joints, I have a whole set of brand new heavy duty ones from Napa - real beefy suckers. Email me if you are interested.
Rob
Rob
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Re: Clunking from rear end after stopping (robzr)
I had this problem 6 months ago and it turned out to be a bad u-joint. The "clunk" only appeared at very slow speeds. I jacked up the back of the car, put it in neutral & spun the wheel. A u-joint was binding up and actually raised the whole trailing arm a few inches and then dropped off.
New u-joints fixed my "clunk". I initially thought my problem was in the tranny too.
--Jack
[Modified by 74jack, 10:49 PM 4/5/2002]
New u-joints fixed my "clunk". I initially thought my problem was in the tranny too.
--Jack
[Modified by 74jack, 10:49 PM 4/5/2002]
