Hum from the drivetrain?

[95BlueStallion]

My car is humming starting at 35 mph, and it sounds like its coming from the rear end. The rear diff is full of fluid, as is the transmission. The hum occurs when I am cruising at a constant speed, it goes away as I accelerate and decelerate. It also goes away if I push the clutch in and coast... My local ford dealer said all my axle bearings are worn out and the rear end needs to be overhauled. If it were bearings in the rear end, wouldnt it hum constantly even when I have the clutch in coasting? Also, my car is '95 with 64,000 miles, would the bearings really wear out already assuming the car hasnt been too abused? Thanks for any input.

 

[1TallMF]

I think they might be correct on this one. From what you're describing it sounds like a pinion bearing issue or possibly carrier bearings or both. Quick test to find this out is to jack-up the rear end, get under there and turn the rear tires slightly foreward and backward. If you see the pinion flange move back and forth at all when you do this, the bearings are probably shot. If you do end-up needing an overhaul, change-out all of the bearings (pinion, carrier and axle) and get a limited-slip rebuild kit, they are relatively cheap. Might as well do it all while its apart.

 

[95BlueStallion]

I also thought it was just the carrier bearing or pinion bearing, but you are right about replacing them all while its torn apart. I guess on the positive side, its a good time to throw in a new ring and pinion!

 

[1TallMF]

I was gonna say get some 3.73's while you're at it, but wasn't sure whether you already swapped gears or not. You won't regret it