Faint Whine in rear

[Tyler.Sandvig]

Hey guys, I got a 1998 Ford Explorer Sport 2dr, 4.0 SOHC 4x4. I just noticed a faint whine today on my way to work. It drives normal and runs normal. The noise isnt noticable up until about 45-65. 65 is about as fast as I go. If i slow the down the whine slows and if i speed up the whine speeds up. Anyone got any ideas? I dont think its the T-case, but im open to suggestions on what to check. Thanks!

 

[jremington59]

Have you checked the fluid level in the pumpkin?

 

[Tyler.Sandvig]

Yupp. Just did that. It was a little low but I filled it now. Took maybe 1/4 quart. Still there. Checked the drive shaft for play to see if it was the pinion bearing. At least that's how someone said you could check it. All the wheel bearings in the back are good too. The only last thing I can think of is the back tires are worn but it does it on dirt roads too.