Diagnosis
A loud thump or grind from the rear is classic failed dryer drum support roller. These are plastic wheels with bearings that the back of the drum rides on. The bearings wear out, the roller seizes up, and you get a rhythmic thump or a constant grinding screech.
How to Fix It
Unplug the dryer. You'll need to take off the front panel to access the rollers. Open the door, remove the two screws at the top of the door frame, then carefully lift the front panel up and off its hooks. The drum rollers are mounted at the lower rear of the drum bulkhead. Spin them by hand—the bad one won't spin freely or will feel gritty. Replace both rollers while you're in there (common kit is part number 279640).
If That Didn't Work
If the rollers spin smoothly, the noise might be from the idler pulley (which tensions the drum belt) or the motor itself. A worn idler pulley will make a high-pitched squeal or chirp. A failing motor bearing has a deeper, more constant grind.
Heads Up
When replacing rollers, also check the drum belt for wear or cracks. A worn belt can slip and cause noise, and it's much easier to replace while you already have everything apart.