When I'm driving through my nieghbor hood at 20-25, It makes a high-pitching whining noise, and it sounds like its coming from the rear end, It goes away at 30-35+. Its been doing it for a couple months now. I think it might be getting louder. Its pretty annoying and makes your truck sound like a piece of junk coming down the street.
Any ideas?

 

water in the rear???

 

If thats the case Im not sure how that happened, I havent driving it through any tall water.

 

when was the last time you changed your diff fluid?

 

...Never It needs it Im sure. Im doing that tomorrow.

 

Sounds like a bad u-joint

 

Yea I've thought about that too. how would I be able to tell?

 

It will make the noise right when you take off and continue to whine at you until you stop... Prob a good thing to replace anyways, not expensive.

 

bad wheel bearings..? just an idea mine were whining like that in the front end when they were going bad

 

Did you figure this out? There's not a lot out there for this, but it seems I'm having the same issue with my truck.