I have attached a PDF file showing the parts list. Have a look at item 33 on drawing as it might not be moving freely causing your issue.
Hi Bruce,
So you think it may be an issue with the drive belt tensioner moving back or forth after being pulled on or released? I can imagine that being an issue with the variable speed not engaging at lower speeds, but would that explain the rear wheels locking up when trying to pull the mower backwards? Or the mower being more difficult to move back and forth when the drive belt isn't engaged?
Cheers,
pau13z