1991 Suburban rear end howling

I have a 1991 Suburban and the rear axle make a whining or howling noise.
I have had it since 2002 and have put 45,000 miles on it and it has pretty much made the howling noise all along.
Is there something I can do short of replacing the gears to quiet it down some??
Maybe a lube additive or something??

Drain it hot and replace with Torco 85W-140. Ideally, remove the rear end cover for full drain (may be metal particles) rather than sucking it out through the fill hole. Reinstall cover (now's your chance to put a chrome one on!) with new gasket or blue Permatex. If you have Positraction, be sure to add the GM Posi lube. too, $8-10 at your dealer.

wolfden6, This may or maynot be related to your problem, but about 2 years ago we heard a growling noise coming from rear end of our 03 Tracker took it to a dealer who found the problem to be a bad wheel bearing on the rear axle. This repair required the rear axle to be pulled which is way more difficult than replacing differential fluid. So if you go ahead and replace the diff fluid and the growling returns ...
Regards,
gb

Hmmmm sounds like the rear differential, pinion bearing.

Chevy 1/2 ton trucks rear ends are notorious for failing.

Switch to amsol, flash point of 1500 degrees, that will never get that hot. They use it in the space shuttles.

It could also be a u-joint. Start simple. U-joints are alot cheaper than a rear end. I have seen u-joints cause howling and grinding noises

Sounds like the ring and pinion gears are out of alignment. If it is louder under load this maybe the problem. If it were a bearing it would have failed long ago. I never heard of a bad bearing lasting 45,000 miles.I'd pull the cover and clean up the gears and then check the wear pattern on the ring gear.

If the ring and pinion gears are not properly aligned how do you correct that problem??

If the R and P are the cause of the noise for this long a time they are worn beyond resetting the pinion depth, preload and backlash. The cover must be removed the gears inspected and as Not Me stated , tooth contact checked, the repair for this type deal is new ring and pinion and proper set up, not a dyer job for anyone who does not have the experience and proper tools.