I'm assuming that you are running singles. If so, don't put the small tire on the rear because the forward and back rear axles are locked together by the driveshaft. The axle with the smaller tire will try to turn at a higher rpm than the axle with the regular tires on it. It will lock up the rear ends and something has to give. It will either break something, skid the tires or hop the axles until the springs break or an axle shaft breaks. If you put it on the front you are ok. The differential will correct for the different tire rpms. The front driveshaft will spin faster than with the regular tires, but the sprag clutch in the TC will let the front axle freewheel. The only problem may be unstable steering/handling. Or, you could put the tire on a rear axle and remove one of the rear axle shafts as suggested above. You would have to have a block off plate to replace the removed axle shaft though