I looked at mine a little bit closer today. Its a Craftman Model 917.272140 20 hp 46" cut. I have the owner's manual showing a parts diagram. It looks like the Steering shaft assembly has a gear on the bottom that syncs up the the sector gear. It appears that the steering gear has jumped a few teeth over so I am running out of sector gear when turning to the right. I have too much sector gear on a left turn and it turns to far to the left.

It looks like the solution (if the gears aren't stripped to bad) is to take of the steering wheel off to access the shaft. Then align the shaft gear with the sector gear so that I have the same amount of steering to left and right. I looked up the parts price and the steering shaft and sector gear are about $20 each.