Went wheeling down at rausch creek when i took my 99 cherokee off the trailer and drove it on the highway there is a loud wine at 55 and over. drained both diffs, filled with 80/90 gear oil still makes the noise diffs looked good. i have a 3" lift on 31s if that makes a difference. dana 30 front chrysler 8.25 29 spline rear. just trying to continue my trouble shooting. tcase? wheel bearing? help please

 

I would drain the transfercase and see what comes out the transfercase and refill with Dextron III or ATF+4... U really shouldn't get a lot of metal so if it is really shiny that probably is the problem and the bearings in there have probably seen better days.

What trans and transfercase to you have?

 

Check ujoints and cardan joint.and tc next.

 

Is there a vibration to go with the whine?

 

A good question here is if you say let off the gas a little does the whine lessen? when the slack hits the slowing down section does it kind of growl and then whine? or is it just a continual whine from 55 on up and same back down till you get below 55.