only my 3rd and 5th gear are wining just started tonight. what could this mean??? l0w tranny fluid???

 

that'd be the first thing to check.....synchros maybe? i dunno....details man....

 

it just started doing it out of the blue tonight im pretty sure its tranny fluid. also i cant find the proper output seal for the passenger side. i have a s21 tranny. all the auto part stores are giving me the wrong part. any suggestions ( its the seal that goes around the axel when you put it in the tranny)