Diagnosis
A grinding noise during spin is bad news. With the shipping bolts ruled out, the most likely culprit is a failure of the spider arm—the large, three-legged bracket that connects the inner drum to the rear bearing and shaft. On some LG models, it can corrode and crack.
How to Fix It
This is a major repair. To confirm, unplug the machine and try to wobble the inner drum front-to-back and up-and-down. If there's significant play (more than an inch or so) or you see rust flakes inside the drum, the spider arm and likely the bearing/seal are shot. The repair involves completely disassembling the tub.
If That Didn't Work
A less severe possibility is a foreign object (like a bra underwire) trapped between the inner drum and the outer tub, scraping during the spin. You might see scratch marks inside the drum.
Heads Up
Continuing to run the machine with a damaged spider arm will eventually cause the drum to detach or seize completely, leading to a much more catastrophic failure. It's a job best left to a pro unless you're very experienced with appliance repair.