Repairs STLX1054 lost drive

Hi all-

Recently had a STLX1054 given to me. Unit starts and runs, PTO engages and operates, but the unit will not move under it's own power. Was told by previous owner that his wife was mowing with it and went to turn and it just stopped moving. He didn't have time or desire to look at it so it was given to me. Releasing the parking brake unit will roll. Just looking for any info as to what or where I should start looking. rearend? hydrostat drive? any info would be greatly appreciated.

Model# 13WK92AK056
DOM 03/2011
Serial# 1C031H60354

Check that the drive belt is on all correct pulleys. Or it broke
You can find diagrams at cub cadet parts n more.com

https://www.cubcadetpartsnmore.com/cub-cadet-service-manuals

scroll down right side of page for your tractor manual, see chapters 5 & 6