Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!
Does it look like the transmission has been out of the mower?
Either the transmission has been apart and the inner differential gear is on wrong side of pinion, or the shiftier is moving the shift lever on the trans mission in the wring direction. With the multiple shift rods, it may be moving lever in opposite direction, See the link below and check the linkage.