It's a MTD Yardman, 17.5 HP, 42" cut; lawn tractor.
(Model 13af688g722 S/N 1c224b40282)
Started to hesitate between speed shifts, then just would not move. Reverse in top gear (8th) moves but ever soo slowly. Forward budges but hits a minor bump and is totally static. Bad belt? Trannie? Adjustment, I'm hoping?

William G. Lawler, July 2009