8.25 Diff questions

I would say something definitely in the r/p setup or bearings. When you push in the clutch and coast, you are narrowing down what it could be. Pretty much eliminating a trans prob.

Before doing anything drastic, I would jack the car up and check wheel bearings, and grab the drive shaft yoke and check for any abnormal movement...side to side and up and down, this is what you're looking for in wheel bearings as well....abnormal movement.

Next would be to remove the diff section. If you get this far, I'm sure your problem will be evident.

The diff is not a demanding build. It's just out of your comfort zone. You can do it!