I get a howling from the rear end. It's usually only when I let off the gas, deceleration, and it only happens during certain speeds usually around 50 to 65 MPH. It goes away br and after those speeds.

I've read that any whirling or howling at any other all speeds can be low pinion preload.

I have. Strange Dana 60. Would the preload have been set from strange themselves?

Is this an indicator of low preload?

Also a vibration that increases with rpms, could be unbalanced driveshaft? Causes rear howl?