Rear end whine?

[Panhead Jim]

94 SR5 3VZE Auto. When I back out of the throttle, the rear gear set whines loudly. Only when I back out, and turns or brakes don't alter the sound. If I apply throttle, she quiets right down. What is it, and what do I do about it?
Thanks in advance for any insight.

 

[fourwd1]

It's probably the pinion bearing, maybe a carrier bearing.
Either way the diff's gotta come out and be looked at by a competent shop. Not every mechanic can set up diff gears properly, although they think they can.

Look here

 

[drmorbius]

94 SR5 3VZE Auto. When I back out of the throttle, the rear gear set whines loudly. Only when I back out, and turns or brakes don't alter the sound. If I apply throttle, she quiets right down. What is it, and what do I do about it?
Thanks in advance for any insight.

X2 Can also be a failed crush sleeve allowing the pinion to move back and forth.