hi i purchased an old 1970's sears 8/32 riding mower model # 536.658060. it runs good and has all 3 forward speeds but no reverse.any ideas? i am a licensed auto mechanic.. but new to the world of tinkering with lawn tractors...this tractor is light enough to get off and push it back if needed ,but it would be nice for it to work properly ...if it can be fixed cheaply.. i have a whopping $75 invested in the tractor and $70 in tune up parts lol

 

Is the shifter moving the full length of travel to put it into reverse, or could it be that something is interfering with the shifter holding it out of reverse?