Originally Posted by 01WhiteRam
I got a humming noise coming from possibly the front differential. While I'm driving above 35mph I start hearing the humming noise. The rear diff has been rebuilt approx. 20,000 miles ago. Is it common for the front differential to go bad?
The 4x4 is rarely used and only for when I'm in snow or possibly some soft ground.
Well answering back to front.
Yes it is common for the front axle to go out, even if you don't have it set for FWD or AWD, the differential still spins unless you are on locking hubs and have them set to free wheel.
Humming noise is usually bearing related, and tracing down exactly what bearing well that is impossible. The only people who can get in your truck, drive it, and listen then tell you what bearing it is are specialist. And even specialist will say and it can be. But you can start by checking the hub bearings, it's a start. The bearings I fear and feel are the problem are the differential bearings because it's a common problem with most axles.