Rear drive terrain/differential noise on acceleration

I have a 1999 GMC Sierra. The rear differential cover was leaking on me for past couple of months, but I was putting it off. FInally this weekend my truck starting making an airplane sound that seemed to be coming from the rear. The sound happened on acceleration only, and increased in amplitude and frequency as the speed increased and as I pressed the gas more. If I let go of the gas, or let it cruise, then the sound would sputter once or twice, and go away. It would resume if I pressed on the gas again.

Since the rear differential cover was leaking, I thought I burned out the gears. When I changed the cover, the gears appeared to be fine. The lubricant was super low, and did smell burned out though. I refilled the fluid and put a new cover on. This did not solve my noise problem though.

Is it still the rear differential that is making the noise? Is it something else? How hard is it, and how involved is it to replace the rear differential? Can I replace its components, and which ones?

Any advice would be much appreciated!

I bet it’s the differential. I would find a used one at a junkyard and replace the whole thing.

You undoubtedly do quite a bit of damage to the components in your rear axle, such as bearings and probably the gears as well, even though you said they look okay. Your best bet will either to take the truck to a mechanic who has a reputation for a high success rate with rebuilding these things and bite the bullet, or replace the whole rear axle with a used one from a salvage yard and hope it’s not bad (they don’t usually go bad unless they are viciously abused or neglected, so your odds are actually pretty good of getting a good one). Replacing the rear axle is not terribly difficult for a fairly skilled DIYer with an assistant to manage this rather heavy, awkward component.

Thank you for the advice guys. Do you think it could be a specific component in there that I could do myself? I do not think I will be able to replace it. I only have my wife to help me, and lifting this puppy under my car while trying to get it in sounds like a project. Plus don’t all the bearings and such need to be aligned?

You most likely burned up your Ring and pinion Bearings… You would need to disassemble the rear and replace ALL of the bearings and inspect the actual integrity of the hear surfaces themselves. Unfortunately this is not as easy as it sounds…bec when they put those rears together they pay very close attention to the gear mesh clearances. I doubt you would be equipped to handle this type of rebuilt.

There are shops that specialize in this sort of thing. Might want to look into that and or get one from a known working vehicle…as swapping the entire rear is a DIY type of job to most wrenches…rebuilding the rear is NOT. You also must be CERTAIN of your rear end’s drive ratios ESPECIALLY if the truck has AWD…a mismatch would be DISASTEROUS… Ask me how I know… LOL. The ratio is usually embedded in the VIN number or other chassis tag OR the tag on the rear itself


The pinion bearings are likely shot along with the carrier bearings. A complete axle from a salvage yard is almost certainly the best option. You would need a shop jack, a good set of hand tools and a level paved driveway. It would be preferable to have some help but with some planning and care the job can be done alone. jack up and support the truck from the frame ahead of the front shackles. After disconnecting the brake flexible line and parking brake cables remove the wheels, put the shop jack under the center of the axle and lift it slightly, disconnect the rear U-joint and wrap tape from end to end over the U-joint cups to prevent dropping cups/needles. Remove the rear shackle bolts and then lower the jack. Remove the U-bolts and pull the jack and axle out from under the truck. Compare the salvage axle closely to the axle you pulled out before attempting to install it. It everything looks OK reverse the removal procedure, inspect the brakes and bleed the wheel cylinders before attempting to drive.

Was there, by chance, a magnet anywhere in the gear case? How about one built into the fill plug? They can tell the story by observing what they have collected…I agree the best solution is to replace the entire axle…Be sure to get the same gear ratio ESPECIALLY if it’s a 4WD…

It would have been much cheaper to fix the leak before the differential was destroyed. The gears might look ok, but could be damaged. Most likely several bearings are shot. If the leak is fixed and it is full of fluid it might go on for awhile and just be noisey.

Find a salvage yard that can source a used axle and see what they would charge to install it. Trying to replace an axle in your driveway with jack stands is a dangerous job. This is a shop job due to extra tools and supports needed to do it safely.

I’ll add this, the pre-loading and meshing in rear ends that use shims is an art that is not easily learned and requires a few special tools. Although I have been successful building a few they were all done at a loss due to my miss judging first one and then another nominal clearance, requiring me to repeatedly tear down and reassemble after a road test. And I had a tool to press the carrier journals open.