Rear End Knocks

Bibbs · March 14, 2005

When letting off on the gas, my rear end in my 1997 Chevy 1/2 ton 4x4 makes a knocking noise. It is much worse at 30 mph or less. I have installed new universal joints even though they did not need to be replaced. The drive shaft does not feel or act out of balance. This noise is clearly coming from inside the pumpkin. When stopping under 5 mph, the rearend rumbles a little but can be felt. What can be causing this? It is getting to the point I am embarrassed to drive it.

GM-Tech · March 14, 2005

Is this a rhythmic knocking as you slow down or a single knock when you let off the gas?

Bibbs · March 16, 2005

It is a rythmic knocking. It doesn't do it all the time but more often than not. I also want to add that I have new rear springs and GM aligned the rear axle and angle. The noise did not go away. As I said, I also have brand new u-joints and the yokes are in great shape. The noise is definetly in the rear pumpkin. Gm mechanic claims he heard no noise when test driving it which is possible considering the terran and driving conditions in that area. He didn't really "test" it. It was late and he wanted to go home. Either that or they do not want to replace since it is still warranted.

Is this a rhythmic knocking as you slow down or a single knock when you let off the gas?

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GM-Tech · March 16, 2005

I don't know if this is your problem, but this type of noise can occur when the carrier is worn where the side gear fits into it. This causes a rhythmic knocking noise that follows the speed of the vehicle, only when slowing down and usually below 30 mph or so.

This problem is easily detected without taking anything apart. Put the truck up on a lift. Grab a rear tire and attempt to rock it. Do not push it straight in and out. Movement and a clunking noise when you push it in and out is normal; however, you should not be able to rock the tire at all. If you can, and it goes "clunk-clunk" when you do this, the carrier is worn and allowing the side gear to have side to side movement. Do this test on both sides, obviously.

Bibbs · March 17, 2005

I will try to check this tomorrow, if not, by this week-end and let you know. If it is the carrier that is warn out, does this mean I have to replace the housing?

I don't know if this is your problem, but this type of noise can occur when the carrier is worn where the side gear fits into it. This causes a rhythmic knocking noise that follows the speed of the vehicle, only when slowing down and usually below 30 mph or so.

This problem is easily detected without taking anything apart. Put the truck up on a lift. Grab a rear tire and attempt to rock it. Do not push it straight in and out. Movement and a clunking noise when you push it in and out is normal; however, you should not be able to rock the tire at all. If you can, and it goes "clunk-clunk" when you do this, the carrier is worn and allowing the side gear to have side to side movement. Do this test on both sides, obviously.

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GM-Tech · March 17, 2005

I will try to check this tomorrow, if not, by this week-end and let you know. If it is the carrier that is warn out, does this mean I have to replace the housing?

The carrier is the part that the ring gear bolts to, it's not the external housing that you see from the outside.

Bibbs · March 17, 2005

So if I installed a Detroit Locker or other posi/limited slip, this would fix it? That is assuming that it is the carrier and it sounds like it probably is. Shouldn't the GM extended warranty cover the repair if I leave it stock?

GM-Tech · March 17, 2005

Replacing the carrier is what's required to fix this problem. The side gears with the planetary gears too. If you replace the assembly, yeah, that would be the same thing and would fix it.

Yes, a GMPP extended warranty will cover this repair. It would not, however, cover an upgrade.