18hp craftsman riding mower model#917.255913. won't turn left!

I have had this problem for the longest time. I replaced the secondary gear twice. Helped for a brief period and now won't turn left again. Replaced the steering shaft and worked for a brief period. Back to no left turns once again. The issue is with the secondary gear and bearings (plastic) which is only a temporary fix. What I had done was welded a piece of steel to the bottom of the steering shaft eliminating the secondary gear connecting directly to the tie rod for the steering. Works perfect now.

You need to get down on the ground and have a look at why it is not turning left. Its as simple as that. A repair will not tell why it is not turning left. Good luck.