Bill, the hex portion was stripped. I taper-ground a 6mm hex driver for a 3/8" ratchet, then drove it in with a small hammer, and staked around it with a center punch and small cold chisel. The threads themselves were fine.
This is the best way to get it out, as you don't want to drill the plug for an easy-out. Too much risk of getting steel shavings in the gear housing.