When was the last time you checked your trans and tcase gear oil levels?
When was the last time you greased all of the u-joints on your rear driveline?
My friend burned up his Pinion bearing in his rear differential, and it sounded like gears were grinding and it sounded horriable.
Jack your rear end up and spin the tires by hand with the trans in neutural. The tires should be able to freely spin at least 360 degrees before coming back to a stop. My friends couldn't even rotate 180 degrees, even if I was he-man.
Is this a 3.0 V6? Or a 2.4 22R-E Pickup? 5speed? Automatic?