Rear end noise
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Joined: Jun 2012
Posts: 71
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From: Suffolk,VA
Rear end noise
Hello. After i have been driving for around 20/30 mins in my 1969, that I hear weird thumping sounds from the rear end area after I accelerate from a stop sign and turn the wheel. Any suggestions? Thanks, Bob in Suffolk,VA
Melting Slicks
Joined: Nov 2006
Posts: 3,412
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From: Apple Valley, MN
Check the snubber bushing that is between the front differential bracket and the frame. You will need to SAFELY get under the car and use a crowbar to assess movement.
Find a parking lot and do some very slow figure 8s. You may have positraction plate chatter that can potentially be addressed by changing the differential fluid and adding 2 bottles of Delco 10-4003 additive.
While you are under the car, check the U-joints and how much stub axle (at the differential) play you have.
Find a parking lot and do some very slow figure 8s. You may have positraction plate chatter that can potentially be addressed by changing the differential fluid and adding 2 bottles of Delco 10-4003 additive.
While you are under the car, check the U-joints and how much stub axle (at the differential) play you have.
Race Director
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From: Sunshine Coast, Queensland, Australia
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Agree, thumping noise from the rear is often the diff snubber bushing. Turning however shouldn't make a difference. Going from forward to reverse should.
Truth is, there are a lot of parts in the IRS that can cause issues. Getting the car up in the air and doing a thorough inspection should be the first course of action. Worn U joints, worn or perished trailing arm bushings, worn diff yokes. Worn or rusted rear wheel bearings all come to mind.
Truth is, there are a lot of parts in the IRS that can cause issues. Getting the car up in the air and doing a thorough inspection should be the first course of action. Worn U joints, worn or perished trailing arm bushings, worn diff yokes. Worn or rusted rear wheel bearings all come to mind.
Burning Brakes
Joined: Jan 2001
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From: Loir Valley Sarthe, France
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I'm going to say that it's the diff clutches. It takes 30 minutes or so of driving for the noise to become evident, that wouldn't be the case with a diff "nose" bush, or probably U/Js.
A change of diff fluid (to a good mineral gear oil and two bottles of GM additive) is a cost efficient first option. Remember to do about 12 figure of eights in a car park after you have changed the fluid, to ensure it's nicely infiltrated into the clutch pack.
A change of diff fluid (to a good mineral gear oil and two bottles of GM additive) is a cost efficient first option. Remember to do about 12 figure of eights in a car park after you have changed the fluid, to ensure it's nicely infiltrated into the clutch pack.
Tech Contributor
Joined: Aug 1999
Posts: 15,175
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From: Connecticut, USA
I'm going to say that it's the diff clutches. It takes 30 minutes or so of driving for the noise to become evident, that wouldn't be the case with a diff "nose" bush, or probably U/Js.
A change of diff fluid (to a good mineral gear oil and two bottles of GM additive) is a cost efficient first option. Remember to do about 12 figure of eights in a car park after you have changed the fluid, to ensure it's nicely infiltrated into the clutch pack.
A change of diff fluid (to a good mineral gear oil and two bottles of GM additive) is a cost efficient first option. Remember to do about 12 figure of eights in a car park after you have changed the fluid, to ensure it's nicely infiltrated into the clutch pack.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Depending on how long it has been since diffy lube has been changed, you may or may not need to do this. But it does sound like you need to add some of the GM Posi additive to the 'punkin'....
If that doesn't resolve the issue, you may have some half-shaft U-joint issue. (most likely the diffy, though)
If that doesn't resolve the issue, you may have some half-shaft U-joint issue. (most likely the diffy, though)
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