Strange Thumping When Driving
Thread Starter
Intermediate
Joined: Jun 2008
Posts: 38
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Strange Thumping When Driving
Hello-
I have a 1987, and when I drive forward, there is a strange thumping sound that comes from the rear of the car. The sound doesn't happen when I move the car in reverse, and after having a broken U-joint replaced, there was no change--and the sound persists.
Could this be a problem with the differential, or as has been suggested, the wheel bearings? The problem just started suddenly and I hadn't done any extreme driving to bring this on.
In a related note, after the aforementioned U-joint was replaced, the ABS activates almost every time I push the brake pedal. The shop who fixed the U-joint said it was because I only replaced one of the joints, and that one wheel was moving faster than the other, causing the ABS to get confused. Can this be solved by replacing the other U-joint, or have the ABS sensors been damaged and need replacement?
Thanks for any guidance on this,
Conrail4022
I have a 1987, and when I drive forward, there is a strange thumping sound that comes from the rear of the car. The sound doesn't happen when I move the car in reverse, and after having a broken U-joint replaced, there was no change--and the sound persists.
Could this be a problem with the differential, or as has been suggested, the wheel bearings? The problem just started suddenly and I hadn't done any extreme driving to bring this on.
In a related note, after the aforementioned U-joint was replaced, the ABS activates almost every time I push the brake pedal. The shop who fixed the U-joint said it was because I only replaced one of the joints, and that one wheel was moving faster than the other, causing the ABS to get confused. Can this be solved by replacing the other U-joint, or have the ABS sensors been damaged and need replacement?
Thanks for any guidance on this,
Conrail4022
Thread Starter
Intermediate
Joined: Jun 2008
Posts: 38
Likes: 0
aminnich wrote:
"First off the shop guys are feeding you a line of BS. Which you joint(s) did you have replaced and why?"
Thanks for your reply. I had the U-joint on the driver's side replaced, and they suggested that both get replaced at the same time, but I didn't follow through replacing both joints, as the passenger's side U-joint was in good shape.
"First off the shop guys are feeding you a line of BS. Which you joint(s) did you have replaced and why?"
Thanks for your reply. I had the U-joint on the driver's side replaced, and they suggested that both get replaced at the same time, but I didn't follow through replacing both joints, as the passenger's side U-joint was in good shape.
Team Owner
Joined: Aug 2008
Posts: 33,025
Likes: 6,538
From: Rochester NY
St. Jude Donor '09 thru '26
After noticing your screen name, the noise could be wear in the rear center plate, or bad snubbers on one of the traction motors. As for the ABS, sound like a problem with the wheel slip relays. 
Le Mans Master
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
OK, time for Corvette 101. There are two half shafts, one on each side providing power from the differential to the wheels. Each half shaft has a u-joint on each end, a total of four u joints. They are sold shafts, so can not be installed out of phase. Wheel spin due to u-joints is impossible and the shop is feeding you BS. Possibly they damaged a wheel sensor, causing an ABS problem. 1. Get under your car and look at the parts I am describing. 2. Find a different shop, the guys you used are evidently idiots, or think you are. Hope this helps.
Thread Starter
Intermediate
Joined: Jun 2008
Posts: 38
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To Railroadman: I enjoyed your post. I knew for sure that when I set up the "Conrail4022" handle that there would be at least someone else here that knows railroads and Corvettes!
To aminnich: Thank you for your replies as well. I believe they did damage the sensor and gave me that story to cover up. I have found another shop that is more competent to say the least (in addition to a lot more DIY). I will check out the parts you described and go from there.
Do either of you believe the U-joints are responsible for the "thumping" problem when the car moves forward, or could that be either the wheel bearings or the differential itself as has been suggested?
To aminnich: Thank you for your replies as well. I believe they did damage the sensor and gave me that story to cover up. I have found another shop that is more competent to say the least (in addition to a lot more DIY). I will check out the parts you described and go from there.
Do either of you believe the U-joints are responsible for the "thumping" problem when the car moves forward, or could that be either the wheel bearings or the differential itself as has been suggested?
Team Owner
Joined: Aug 2008
Posts: 33,025
Likes: 6,538
From: Rochester NY
St. Jude Donor '09 thru '26
IMHO, if it was a u-joint problem you would have it in both directions. I'll defer to those with more experience on the wheel bearing vs. differential question.
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