Hello everybody!

So I'm totally confused about this noise. Video posted below the text.
Whirring/whining noise when decelerating only
This noise is normally indicative of a bad pinion bearing on the differential...however when I was diagnosing the noise it changed.

1st. I changed all fluids, and a roller bearing came out of the transfer case. Fluids were good in front and rear diffs. Had Austin Rover Works put in a known-good transfer case and he re-sealed it and warrantied it for 12 months.

2nd Noise was still there after transfer case swap. Austin Rover Works said they heard no noise after installing the T case when the tech ran it on the lift. A few months later, I diagnosed further at home be removing each drive shaft, and driving.

3rd Front drive shaft removed = no change in noise.

4th Rear drive shaft removed = noise CHANGED! The pitch of the noise is the same but now it was at all speeds.Slowing and speeding up. Gets louder when speeding up and quiter when slowing etc...The noise is more indicative of wheel bearing or tires.

5th rotated tires and drove without rear driveshaft again = no change in "new" noise.

I'm going to put the rear driveshaft back on in the morning and drive again. I THINK its going to be something in the transfer case or maybe the pinion bearing in the diff and I suspect that having the rear driveshaft in place puts strain (added rotational mass) on one or the other enough to make this noise.

Thank ya'll for your help!

I have TW front and factory rear driveshaft and am at about 4.5in lift.
Video:

 

Noise is back to original type of sound after re-installing rear driveshaft

1 Changed rear diff fluid just “in case” and noticed nothing on the magnet, the fluid was goldish color (as normal) and did notice the fluid seemed aerated.

Also found very small brass colored metal filings in the pan. I am not aware of any brass in the diff gears so I’m not sure what that’s about. Investigating.

 

It's too hard for me to distinguish between cabin rattles and the noise you're wanting us to hear. I had my front differential grenade itself on the freeway after yelling about it for a couple days. It sounds like a banshee. I don't hear that in the vid, so might be OK ruling out the diff. For now at least.

 

Update 3: the “brass” was just fine metal particles that looked brass colored in the sun.

Drain the transfer case and found the dark grey to black fluid. Refilled with fresh fluid and it still has the noise.

The transfer case was re-sealed in Nov and they used black rtv to do that. I’m hoping the fluid was dark because of that maybe? I have only driven about 12k miles since the shop resealed it.

Just to be sure, I checked the serial number on the case and it definitely is different than my old one so I know they replaced it.

at this point I’m going to take it to the shop and have them diagnose

 

Looks like you tried almost everything. In the vid: sounds like rear diff.... when you let off the gas, the torque changes and the sound changes

 

No. RTV won't change the color of the fluid.

 

The only thing that jumps out at me is..."a roller bearing fell out of transfer case". This is not normal.

 

Yea, thats why I had the shop replace the case.

Thank ya'll for your help

 

So I took the truck to my local Rover shop (Austin Rover Works) and went on a test drive with the master tech Ken.

He believes the noise is the rear diff. I bought a front and rear diff from them off of an 03 D2 that was not lifted and had a front end wreck. Going to install the rear this weekend and see how that goes.

 

really? Gtfo