I have a 92 Trooper, automatic, and the rear differential whines----a lot. I pulled the rear brakes, pulled a rear axle and the axle bearings feel tight and smooth when you rotate the axle. I disconnected the driveshaft, started the car and the tranny and transfer case are quiet. A stethoscope on the rear axle housing sounds like a lot of gears whirring. In reverse it makes less noise. When I first start it up it takes it about 10 seconds of being in gear before the noise starts. Fluid is good and new. I was told thrust washers maybe or ring/pinion gear or ???? Also where is a source for parts and a manual.