Reverse issues on 904 transmission

So when I start my 72 Dart with a slant 6 and 904 transmission and I put it into reverse it makes a clunk noise and the car jerks real quick. Also it seems like reverse doesn’t work very well until the car is warmed up fully. The car sat for 24 years but I changed the transmission filter and fluid last year. So I’m guessing the bands might need adjusted?