Silverado rear end... metallic, dragging noise.

[mrsilv04]

OK, I've had it. I have a metallic, dragging noise on the rear end of my 2004 Silverado, 2 wheel drive, 3.42 limited slip. Changed out the rear pads and rotors with no change. The emergency brake shoes were good when I changed out the rotors. They had plenty of friction material left on them.

Sometimes, when it seems louder than usual, it will decrease in volume when I lift my foot off of the gas pedal. It will also change in tone when the suspension compresses and decompresses (like a dip in the road). When I put it into reverse to back out of the garage, there's no play in the drive line, so I don't think it is a u-joint, there's no clicking either in a turn.

I lost a u-joint on the Sierra, and this doesn't seem the same at all.

My neighbor thought that it sounded like it was coming from the passenger side. My best guess at this point is to suspect an axle bearing?

 

[Doog]

Rear diff pinion bearing is shot. (my guess) should make a tone on accelerator dip in at freeway speeds. When you let off the accelerator pedal it quiets? Have a mechanic put a microphone on the rear diff and see.

BTW have you checked your rear diff oil level?

 

[cathy]

How do you have a mechanic put a microphone on the rear diff?

 

[The Critic]

Originally Posted By: cathy
How do you have a mechanic put a microphone on the rear diff?


You use a wireless chassis ear:

http://buy1.snapon.com/catalog/item.asp?...re&tool=all

 

[browning300wsm]

Originally Posted By: Doog
Rear diff pinion bearing is shot. (my guess) should make a tone on accelerator dip in at freeway speeds. When you let off the accelerator pedal it quiets? Have a mechanic put a microphone on the rear diff and see.

BTW have you checked your rear diff oil level?



if the rear diff pinion bearing is shot the oil seal will leak and diff will loose oil ..can you see oil seeping on the pumpkin ????? the best and easiest. check the oil level in the rear diff ...

 

[The_Eric]

Don't these have the rust prone backing plates that like to rub the drums/rotors?

 

[mrsilv04]

When I replaced the rotors, the backing plates were good. Still solid with the paint still on them.

I have a wash bay in my garage. I don't let salt sit on this truck.

 

[mrsilv04]

Pumpkin is clean. Not even a sign of a seep anywhere.

 

[mrsilv04]

To follow up and to hopefully help someone else out with a similar problem... it was a bad carrier bearing.

 

[George7941]

Good to know. I have a Sierra myself and will keep this in mind. No noises so far from the driveline.

 

[mrsilv04]

Mechanic said that he's seen carrier bearings go bad before on GM trucks, but mine is by far the earliest failure that he's personally seen (78,000 miles).

 

[George7941]

After I posted I realised that I have a one piece driveshaft with no carrier bearings, so nothing to worry about on my truck. However I do work on other trucks, some of them with two carrier bearings, and will keep your description of the noises in mind when trying to diagnose driveline noises.

78000 miles is low, do you have a heavy foot? With 2wd I expect you don't off-road.

 

[wtd]

I have a 98 chevy 4x4 that I bought new. I changed out both diffs at 20,000 miles and used Mobil 1 diff fluid in them. At about 55,000 miles I was getting some type of noise coming from the rear but didn't know what it was. Finally at about 75,000 miles when the noise was getting louder, I took it to a driveline shop and they discovered that my pinion and carrier bearings were shot.

This was on a truck that hardly ever towed anything and when it did it was only a 5x10 utility trailer. It also never hauled anything heavy. Mechanic told me that the 10 bolt diffs were built with undersize bearings. Truck now has 125,000 miles on it and rear is still quiet as far as I can tell. I also went back to a conventional diff fluid since that is what the diff called for.

Wayne

 

[AMC]

Gm trucks are known for driveline issues. Generally there are a couple of easy fixes. If you are getting driveline clunk when going over bumps, You can lube up the slip yoke and add spring clamps to the leaf springs and that generally fixes that issue. Carrier bearings and U-Joint problems can generally be solved by replacing them with aftermarket parts that have grease zerks on them. Other general problems with the rear end can be reduced by changing the rear differential fluid every 30,000 miles or so and replacing the shocks if they go bad. Installing spring clamps 6-8" in front of the rear axle helps control the movement of the springs in that area if they get worn out and soft. If the rear axles flexes too much because the leaf springs are soft, that will cause noise and other problems.