Jack the rear wheels off the ground. Put the car in neutral. Tighten front band adjustment till driveshaft will not turn (not cranked down tight) then back off 3/4-1 turn. Repeat for rear band. Rear band adjust ment will not affect shifting except into low 1 or reverse.
Now your bands are adjusted.
I will add that when you turn driveshaft in reverse direction it will be noticably harder to turn, this is normal you are fighting the sprag/overunning clutch/breakaway clutch/rollery spring thing in the back, whatever you chose to call it.