Looks like Weingartz has a complete diagram here.
https://www.weingartz.com/assembly-diagram/john-deere-parts-lookup/model-la175-tractor-pc9747-mower-drive-belt-sheaves-spindles-blades-mower-deck-and-lift-linkage/4275-36365-530289
That's it! A little stick jumped up there and threw the belt off the left hydro pulley. Nice diagram on Weingartz showing the belt path. Found a Youtube video on how to back off the tensioner to slacken the belt and get it back on the pulley.
Thanks!
