Help diagnose rear end noise please

Guys,

I have recently developed a slight rear end noise. It's between a low whinning and grinding noise. At first I thought it was my rear diff but the more I drive it the more I think it might be the pinion bearing. I have not had time to get to it but I plan on changing the diff oil and inspecting the gears and look at the pinion bearing also this weekend.

I am just wondering what else it could possibly be. When I drive it the noise starts to be noticeable at about 20mph and gets louder the faster you go (to a certain point but never loud enough to be heard over a radio or anything), however, when I let off the gas the sound near dissappears and there is a momentary delay where there is not noise. Then when I give it gas, it comes back. This got me thinking that is was not my rear diff because that would be a constant noise so I am starting to think it is the pinion bearing (which is new, just replaced this mid summer) or possibly driveline u-joints.

I have never heard u-joints make this sound before so I don't know if that could be it or not.

Any suggestions/ideas/thoughts?

thanks a bunch

Probably pinion bearing. I had that noise on a YJ once, costed me 700$ to get a D35 rebuilt.....

Don't waste any minute and check this, If you let it go too long it can eat your gears

it sounds like it is a rear pinion bearing. If it is only whining under acceleration it sounds like a bearing. Pull the cover and check your gears and diff fluid ASAP so it might not possibily be a lerger problem then thought.

also wanted to add, the title you posted made me laugh for a second....... rear end noise huh huh...

Check fluid level as mentioned. If major damage has occurred then just look for another rear. Because there are a ton of them for sale cheap. A lot cheaper that rebuilding yours.