Sometimes it's the little things that get you. Like a set screw.
Sometime during the night it dawned on me that if the drive motor had quit the whole slab saw would shut down. So it had to be something else.
It also occurred to me that the drive motor is attached to the driveshaft with a single set screw.
So a while ago I pulled the housing for the drive motor off.
I was correct--it was the set screw.
I took the housing off and the bushing just fell off the end of the driveshaft and into the housing. I cleaned it up with Shooter's Choice degreaser, put it back together, and it's out there chewing on a really neat piece of agate that is dendritic on one side like Montana, and grades into a golden amber on the other side.
The one problem with all of this it that the thing is so old that a little oil seeps through on the driveshaft and lubricates everything, including the set screw. So it's not a question of "if" it happens again, it's a question of "when."
The distance between the motor and the cabinet of the saw is also so tight that you can't get a regular Allen wrench in there--it really needs one about 6 inches long.
I didn't have any Loc-tite, so next time I go to Home Depot I'll get some, and also look for a long Allen wrench in the right size so I can get some torque on it.
While I was at it, I took the tumbler apart. That one's easy. The motor is shot. No biggie--$14 at Graves. Cheaper than buying it from Lortone.
But that said, I surely do like my Lortone equipment.