Wish i could go backwards

My trans sucks and i don´t have the cash to drop in a new one so i´m tring to fix the one i got but i can´t find the problem. the is no reverse, nuteral is low. Its not the linkage. overdrive, drive, second, and low work fine. i changed the filter and found no shavings in the pan to indicate that the bans are worn. anyway im stuck anyone that can help please do