Thanks SO much for the information!! Went back in yesterday, put a scant amount of grease on that worm gear, and on the shaft of the hand wheel. Might have helped a bit, but he's still pretty growl-y. But... his top speed is pretty impressive for all that. I hesitate to run him for long with that noise, but maybe it's normal for the machine? Have heard mention before that these guys do tend to run noisy.
I think my take away was: don't fear the lube. (Except on rubber or plastic bits, of course, but that's another issue.)