2002 Chevy 2500HD Rear End Noise?

Question

My truck makes noise when you get between 70 and 80 or when you are letting off the gas pedal to slow down a little. It is by far the worst at around 80mph. I have had gm look at it and they told me same thing as my mechanic. Which he has changed the pinion bearings, and it still makes the same noise. What else could it be?

Truck is extended cab. The noise sounds like a bearing to me. But it does not make it all the time. It is like a growling noise.

Answer 1

what type of sound? does your truck have a center support bearing? some of the crew and extended cab trucks use a bearing on the drive shaft that can go south and make some goofy noises

Answer 2

There are a few things that would have been noticable had the rear pan been pulled and the differential removed to replace the pinion gear bearings. This whole process is not a job for your Joe Blow mechanic.

You have to know how to crush the seal/washer on the pinion gear but more importantly setting the gear lash between the ring and pinion gears. Some folks just never read into it or invest in the tools required and end up chewing the teeth off of the ring gear.

Here's how the whole rear end works:
The ring gear forces gear oil into the axle tubes and it reaches the wheel bearings and then runs back into the differential casing through the differential bearings. The most common bearings to fail are the axle bearings since they take more punishment and are more distant to the gear oil. Some folks think a gear oil leak in the brake drum is the rubber seal but it is very much like the engine main seals that leak when the main bearings wear and the crankshaft vibrates more and then settles at rest putting stress on the seals.You can replace seals every six months and this will not center a crankshaft nor will an axle seal repair a worn wheel bearing.

If it isn't the U-joints, driveshaft removed, u-joints replaced, driveshaft pressed and rebalanced, then it may be one of the other bearings in the rear end except that this should have been obvious during your last service as there would have been an excessive amount of metal in the diffential housing.

I'd focus on the rear u-joint.and driveshaft before I spent any more money on the internal bearings.

Make sure they added the tube of gear oil additive specified by GM or you'll get a new problem down the road.

If you do end up taking the whole rear end apart make sure they flush out the axle tubes before doing anything else. Metal residues collect in the tubes and it's fruitless to spend money on rebuilding the rear end and throw it back together with all that residue still in the axle tubes and differential housing.

An easy u-joint test you can do on level ground is to sit on the bumper, tranny in park, and push with your legs and rock the truck back and forth. There shouldn't be any excessive movement or noise when you do this. If the truck moves more than two or three inches and you hear an audible clunk or similar noise, you have a bad u-joint and should do the aforementioned services at a shop that handles driveshafts, exclusively.

If you do any extensive rear end work, the whole rear end should be removed and taken to a shop that handles rear ends, exclusively. If they do 18-wheeler drive axles/differentials then this is the place. Here in Indy I go to Power Train of Indianapolis. All they do is rear wheel drive assemblies and give you a six month unlimited mileage warranty.

Good Luck!