1973 plymouth duster help

i just driving my duster around. i backed out of the driveway today and when i came back and parked it again it wont go into reverse anymore. it will go into drive and park. so i dont know if it a cold problem because its been below freezing for a couple days now but i got the car warmed up so i dont know what the problem is i just wanted to see if there is something i could go and do before taking the transmission to the shop
Author: kpetty105