While doing some maintenance last week I found that the ground drive belt (engine to transmission belt) was in bad shape about ready to break. I ordered a new belt and installed it a few days ago.
I had mowed once on the old wore out belt prior to installing the new belt and it drove fine with no problems.
Now the problem : With the new belt installed, the tractor will initially move forward or reverse for awhile but then slows down and quits moving altogether as if the clutch or transmission (hydrostatic) quit working - let it set for awhile and it and is OK until it quits again. And the brake doesn't seem to be working very good either.
After it quits, Have somebody else try to drive the mower, while you,look and see if the belt is turning, and where it is slipping at. I suspect there is a problem with the belt slipping, after it gets hot. Maybe sears superceded the belt to something that doesn't grip the pulleys properly.
