1000 hours is about the life of the hydros on the 100 series JD's
So try pushing it without the bypass lever in the push position.
The wheels should lock if the hydros are in very good condition
If the mower moves with a lot of effort then stops the instant you stop pushing then it should run
If it pushes with little to no effort and will roll on when let go the trans is deceased.
A common trick is to remove the belt then say it broke to hide the fact that the hydros are gone .