Clunking/grinding while braking?

I have the truck listed above with approximately 135,000 that is making a clunking or grinding noise coming from the rear axle when the brakes are applied with light or moderate pressure. The noise is cyclical and follows the wheel speed. So as the speed decreases the cadence of the noise slows down.
If you release the pedal the noise goes away, and if you press harder the noise goes away. With the vehicle in reverse, it won’t make the noise at all.

The brakes were done last summer at a shop, but they made a high-pitched squealing noise pretty much from day one so it had to go back several times before they got it sorted out. I pulled both rear wheels off and the pads seem to be wearing evenly and are not bound up in the caliper brackets. I checked all the bolts, and they are tight.

A different shop in town diagnosed it as a bad bearing in the differential but did not pull the cover. I am wondering if this is just bad brake parts, a warped rotor, or if it could actually be a bad differential bearing. Any advice or additional things to check would be appreciated.