Noise in right rear wheel of 72 coupe

[Bill S.]

I have a 72 Corvette coupe with a 350 engine and automatic transmission. I had replaced my power brake booster and after a couple adjustments the brakes functioned properly. I do not have a lift so I jacked each wheel up separately to bleed the brakes. While bleeding the rear brakes I noticed the right rear rotor was slightly scored so I replaced it. I then thought I would adjust the ride height in the rear so I lifted the car by the differential and replaced the rear spring mount kit with a NOS GM one which consisted of two bolts with associated washers, cushions, cups and nuts. The new bolts were longer than the original ones in the car and the rear of the car then rode higher than when the original shorter bolts were in place. I then operated the vehicle. When I put the car in gear and start to go I now get a klunk noise which seems to repeat with each rotation of the tires. This noise happens if the car is in drive or reverse. My wife listened for the noise when I drove it down the driveway and she said it seemed to be loudest in the area around the right rear tire. After a couple runs up and down the driveway I removed the rotor on the right rear brake and did not see any signs of rubbing on it. Any thoughts of what is going on?

[Joe L.]

Re: Noise in right rear wheel of 72 coupe

I have a 72 Corvette coupe with a 350 engine and automatic transmission. I had replaced my power brake booster and after a couple adjustments the brakes functioned properly. I do not have a lift so I jacked each wheel up separately to bleed the brakes. While bleeding the rear brakes I noticed the right rear rotor was slightly scored so I replaced it. I then thought I would adjust the ride height in the rear so I lifted the car by the differential and replaced the rear spring mount kit with a NOS GM one which consisted of two bolts with associated washers, cushions, cups and nuts. The new bolts were longer than the original ones in the car and the rear of the car then rode higher than when the original shorter bolts were in place. I then operated the vehicle. When I put the car in gear and start to go I now get a klunk noise which seems to repeat with each rotation of the tires. This noise happens if the car is in drive or reverse. My wife listened for the noise when I drove it down the driveway and she said it seemed to be loudest in the area around the right rear tire. After a couple runs up and down the driveway I removed the rotor on the right rear brake and did not see any signs of rubbing on it. Any thoughts of what is going on?

Bill------


First of all, if the bolts in the GM kit you used were 6-5/16" in length, those are the correct length bolts. If your "original" bolts were significantly shorter than that, then they are not original to the car or correct.

As far as the noise you describe goes, it could be several things. This includes a half shaft u-joint problem or, even, a rear wheel bearing problem.

[Tom M.]

Re: Noise in right rear wheel of 72 coupe

When you replaced the rotor, how closely were you able to set the runout?

[Mark E.]

Re: Noise in right rear wheel of 72 coupe

"The new bolts were longer than the original ones in the car and the rear of the car then rode higher than when the original shorter bolts were in place."

Are you sure? Longer bolts lower ride height.

Longer bolts also decrease clearance between the tire and spring, so check that.

Other things to check: bent backing plate, rotor runout, tire rubbing on something.

[Edward J.]

Re: Noise in right rear wheel of 72 coupe

Bill by chance did you adjust the E/brake to tight when you installed rotor.

[Bill S.]

Re: Noise in right rear wheel of 72 coupe

Joe,
Thanks for the reply. When I used the word, "original" I meant they were the original bolts on the car when I bought it 20 years ago. They were shorter than the correct bolts (GM part # 3831585) which I installed. My GM parts book states they are 6-1/2 inches long. The folks writing the parts book probably rounded up.
Thanks again for your response.

[Bill S.]

Re: Noise in right rear wheel of 72 coupe

Ed,

Thanks for your response.
I did not adjust the emergency brake after I replaced the rotor on the right rear brake. The klunk noise is quite pronounced but only repeats once at each rotation of the tire. Could the emergency brake shoe be interfering with the rotor as the rotor turns?

[David H.]

Re: Noise in right rear wheel of 72 coupe

Bill

By chance did you replace your rear shocks?

Dave

[Bill S.]

Re: Noise in right rear wheel of 72 coupe

Dave,

Thanks for your reply.

I did not replace the rear shocks.

Bill

[Edward J.]

Re: Noise in right rear wheel of 72 coupe

Bill,If the machining of the rotor was not done properly from factory or even stacking of pallets with the weight this will warp rotors. you could have a high spot on the inside surface,or even the mating surface a has some rust.cleaning of the hub is always Recommended.