For those who have a toe-out problem with their Sears lawn tractor, I feel your pain. I had the same problem, with the additional problem of the front wheels coming off while cutting . My lawn tractor is a 54 inch cut machine. I has two linkages on each side, a long link from the steering gear to the front axle, and a short linkage running from a plate connected to the front axle to the front wheel. Replacing the linkage might solve the toe-out problem for a while, but it will return as the linkage ages. The solution requires some fabrication, but it isn't too bad. The linkage rods are made of normal steel (not hardened), so they can be modified. My solution was to put rod ends (Amazon, Summit Racing) on each end of the linkages to allow for adjustability, but eliminate most, if not all, of the play in the linkage. Rod ends are usually made with National Fine threads. I found the long linkage has too many minor bends in it to support putting a threads on either end, so I have to bend new linkage rods (5/8 inch rods, but I think one could use 1/2 inch rods). For the short linkage rods, I went to a 3/8 stainless steel threaded rod, but I had to increase the length in order to get the adjustability I needed. Adding a piece to the pivot plate connected to the axle took care of that. I maintained all of the current linkage connection point holes at the factory size (3/8 machine bolt fits just right). Just replacing the short linkage with the rod ends and the threaded rod fixed most of the toe-out problem, and I still have room to make finer adjustments. The pivot shafts for the rod ends are 3/8 inch by 2 machine bolts with the unthreaded part ' hosting' the rod end. One nut threaded all the way down to the unthreaded part, and a second nut to connect the linkage to the existing connection point. I just got the bender to make the longer linkage bars, but I haven't actually make those yet. Some bushings are going to be needed to allow the 5/8 inch rod ends to work with the 3/8 bolt shaft. I still have to extend the steering stops a bit to limit the sharpness of the turn the lawn tractor can make. As far as the wheels falling off, the E-clips that hold the wheel on the axle don't make it. After a few tow-ins, followed by repairs, I drilled a 1/8 inch hole through the axle (they're case hardened, you'll need a carbide bit) and put a spring pin (TSC) through it. I haven't lost a wheel since, and the toe-out fix has taken most of the side play/force out of the wheel.
I can give your more details if you're interested. Use: edrews1, Subject: Lawn tractor steering, domain: yahoo.com. BTW, my neighbor has a Sears lawn tractor, but the linkage on his is different. You may need to adjust the fix above to accommodate differences in your steering linkage. Not including the tools, I probably have $25 - $50 in parts and materials.
One other hint: don't modify the existing connection points or other hardware in making your fix. If your fix doesn't work you can always go back to the old linkage. Also, those adjustable linkages didn't fit my lawn tractor. They also have the same type of connection hardware as the non-adjustable linkages, so you'll be adjusting the length as the connections loosen up. I also had one of those connection points come apart on me.