12 Bolt Rear End Noise Chevelle Need Opinions

[626Chevelle]

I had my 12 bolt rebuilt with a used eaton and ring and pinion. The builder stated that the eaton clutches were good, but the ring and pinion was worn out uneven. A new U joint was also installed. It is a 12 bolt with 3.73 gears. I also installed new rear brakes.


The noise is there between 0-15 MPH both accelerating or stopping. It doesn't matter. Even when I coast at that peed. Once I gain speed, the noise disappears. Also, when I drive the car cold, or for the first 5 or 10 miles, there is no noise.


Here is a link I recorded of the noise from the rear end. It's a suttle harmonic noise.


http://www.youtube.com/watch?v=WyXssm6q3VM


Is it bearings, the ring and pinion, new rear brakes? I have no clue.

[andrewb70]

It sounds like the noise is at tire speed. Are you sure that nothing in the brakes isn't rubbing? What kind of new brakes did you install?

Andrew

[626Chevelle]

The rear end shop installed some cpp brakes, drilled and slotted 12" rotors one piston calipers. My buddy thinks its the brakes too.

[andrewb70]

The rear end shop installed some cpp brakes, drilled and slotted 12" rotors one piston calipers. My buddy thinks its the brakes too.

It could be a warped rotor, or maybe a caliper bracket that isn't quite right. Without seeing it, it's hard to say. Since it doesn't make the noise when cold, I suspect something is rubbing after things warm up, due to various metal parts expanding.

Keep us posted. Everyone loves a good mystery.

Andrew

[626Chevelle]

Thanks for the suggestions. I appreciate it. I'm going to check those out within the next couple of days.

[Z06vet]

May have to shim the caliper if its not centered. I had a noise from my C5 rear brakes and had to add 1 more shim for clearance. Most times I have gear or bearing noise its in the 40-50 mph range at a constant cruise speed.

[TheJDMan]

Sounds like brakes to me too. There are a couple of things I would do. 1. Pull the rear wheels and see if there are any witness marks on the rotors from something rubbing. 2. Find an isolated stretch of hiway and make a series of hard stops from hiway speeds to get the brake pads beded then see if the sound changes.

[626Chevelle]

I had a bent axle! I didn't feel anything either. I raised the rear end and noticed a wobble. Axle is replaced and the noise is gone.

[andrewb70]

I had a bent axle! I didn't feel anything either. I raised the rear end and noticed a wobble. Axle is replaced and the noise is gone.

Thanks for the update! Glad you figured it out.

Andrew

[Killi Nova]

I had a bent axle! I didn't feel anything either. I raised the rear end and noticed a wobble. Axle is replaced and the noise is gone.

Glad you have solved the problem. We are getting exactly the same noise from the rear end of my friend's 74 Nova with CPP big brake upgrade.
Was it bent axle shaft, flange or tube?

Thanks