The carrier bearings could be going bad. I had noise from my diff on my 98 Chevy 1/2 ton, and it was a carrier bearing going bad. I got noise at highway speed just driving and under acceleration. The guy that did my diff on that told me that ring and pinions rarely go bad. Usually it is a bearing that eats it.

One way to test if it is the ring and pinion is when you let off the accelerator, does the noise get worse (deeper growl)? If so, this is the ring gear pulling the pinion to it and letting you know there is a problem with the gears.

When you accelerate, the ring gear pushes the pinion away, and noise there is usually a bearing (pinion bearing) going bad.

When my carrier bearings were replaced, the gears looked great and guesses indicated that I had about 3,000 miles left on that carrier bearing before it was going to let go.

For testing/checking wheel bearings, drive the truck down the road and swerve (turn steering wheel) from side to side. This loads the bearing and if that bearing is going bad, it will make noise. If you swerve left, you are loading the left wheel bearing, and swerving right loads the right wheel bearing.

Remember, you have carrier bearings (for the diff) and also a set of wheel bearings out past that. IF the seals on the diff are going bad, you can get them leaking...Also, there may be two sets of seals per side (a seal at the diff and one at the wheel) on these trucks, I just don't remember, sorry....

Another thought is that you need to inspect / change your u-joints. Not for the fluid leak, but the noise and feedback.

Hope some of this helps....
James

Let us know what you find....