2002 Suburban 1500 4wd Axle Hum?

[smams1962]

changed front diff fluid, changed transfer case fluid, changed trans fluid. I have not changed rear diff yet but it has history as being low on fluid at oil changes. No sign of leakage. What can be humming in rear diff??

[McLeod]

changed front diff fluid, changed transfer case fluid, changed trans fluid. I have not changed rear diff yet but it has history as being low on fluid at oil changes. No sign of leakage. What can be humming in rear diff??

The fluid has gotta be going somewhere...either leaking out the pinion seal, the cover gasket or around axle seals. While there's always gonna be some gear noise, you may have some bad/loose bearings in the differential...or, depending on miles and use or running with low fluid there could be significant ring & pinion wear. ...keep driving & listening for it to worsen (or, hopefully stay the same) or pull the cover and take a look (&, look around the axle flange areas for leakage of the axle seals). Good luck. Mc