I know I'm bumping this thread, and for that I'm sorry, but I still haven't fixed my problem. I have been too busy to work on the pinion angle, but I'm starting to think that's not my main problem. What I'm hearing sounds like a metal on metal grinding almost. I have always thought that it sounded like worn brakes, but it doesn't stop when I press the brake pedal. And when I rotate the wheel with the car on jack stands I don't get any noise. I am even more convinced now that it's brakes because it gets MUCH worse when it rains. We have been hammered with storms down here for the past month, and Saturday it was really bad. When I got in the jeep to drive to church yesterday, it did the typical drum brake sticking after wet, but my noise was also significantly louder.

I'm going to pull apart my brakes in the next few days to see if that's the problem. I'm just also inclined to think its not because of how the noise changes depending on throttle position. When I am coasting its the worst, and sounds like rubbing brakes, metal on metal, and is kind of sporadic. When I'm accelerating its a pretty steady scraping. When I'm just cruising, sometimes I get a worse scrape when I hold the throttle at like 1/4. It's weird, but something will fix it...

 

It could be the brakes or both. Good to check them both anyway. When u-joints are out of alignment and yokes/pinion are at extreme angles (from your photo, you're in this territory), you can get metal on metal/grinding/humming/rumbling/squealing sounds or any combination thereof. It could also be bad u-joints or pinion bearings. Even if they are new u-joints (I've had dozens bad out of the box). All depends on the Jeep. The driveline is part of a system. Any failing or failed link(s) in the chain adds up. Not all problems generate the same noises.

 

Same problem on 01 with 228k miles....put a 6.5" lift and it got even worse because pinion angle got worse. It is your pinion bearing and gear lash. Good reason to regear. Cost me $500 on axle to regear. When they took the rear diff off they lifted the wheels off the ground and got it up to about 45mph and then let off the gas and it was bad. The gears seperated and were barely touching causing that horrid noise. It sounds like a J brake off and 18 wheeler.

Jack the rear up.....have someone give it some gas while you are under it....hold the tail of the diff and you will feel horrible vibrations.