175 bACKWARDS

new member here i have a problem guy gave me a 175 that someone took trans apart and reinstalled and trans runs backwards foward is reverse belt and linkage look ok is there anything inside that could be installed wrong runs great and pulls great with no noises belt is right is there ANYTHING inside the transaxle that could be installed wrong? it was taken apart not by me so i dont know what was done inside last owner used it that way till he got tired of it thats when i got it any idea were o start ?i did just reverse belt the wrong way and it worked but belt rubs and its not right