I recently bought a house, the sellers included the Sears Craftsman Riding Lawn mower, Model 917.254750. At closing they said it had been sitting for at least a year. Sure enough the batter was as dead as a door nail. I charged it up. 3 of the tires were dry rotted. I replaced them. Note to others, When removing the rear tires do not loose the square key. with out them it will not move. The only problem I have right now is I can't get the mower to go into reverse gear. I am open to suggestions. For a free mower this thing is really starting to eat up the wallet. Thanks

 

The shifter bent, it's probably stiff and hard to shift, right? It needs to bend back forwards. Some models have an adjustment for it, some don't. Bend it forwards so that it can move the selector far enough into reverse.

 

One of my lawn tractors (a 1983) is similar to yours and also uses a 5 Speed Peerless TransAxle (813B) that I recently had to disassemble and replace a few parts.

Yours is represented in the attached schematic:

CRAFTSMAN 917.254750 Owner's Manual (Page 42 of 52)

I had similar difficulty shifting, and it was as simple as replacing the worn bushings (#34 and #36) at the ends and midway along the Countershaft (#4).

Hopefully, you can correct your issue externally, as Cheese suggests, without removing the transmission; but it's not as big a deal as it might appear. The hardest part is identifying which parts actually need replacement and locating a source . . . . eBay has served me well.

The above link should also serve to give you access to the entire 52 Page Owner's Manual for your Unit.