Humming @ 65 mph (Rear)

[4x4username]

I hear a humming noise- starts at 60 mph and and ends at 70 mph. Seems to be coming from rear.

99 Explorer XLS, 2 WD.

Obviously driving at speed limit (65 mph) is a problem
for me. Any suggestions apart from driving faster?

 

[Jason_25]

Check the front of the rear axle and see if there is fluid leaking from where the driveshaft runs into it. If so, your pinion bearing could be on it's way out.