Sounds like the rear axle limited slip clutches are grabbing to much. To repair this the clutches will have to be replaced. You will also want to verify the front hubs locks are not trying to engage.
Hubs will make a clicking popping noise
Clutches will make a groaning moaning noise and sometimes they produce a slight driveline vibration.
Here you go don't forget to add diff fluid
No the posi trac which is actually called limited slip has nothing to do with the 4x4. It is just a clutch pack in the rear axle that tries to make both rear tires spin in mud and snow.
If one hub was locked in and one was not this can cause front axle and wheel bearing and lock in hub problems. The SD 4x4 sytem is not made to operate at high speeds with the hubs locked in. It will get to wobbling internal in the hub bearing and just shake all the bearings to pieces.