727 no reverse

We are finally are at a point where we can drive the car around the block. We started it, checked the fluids, put it in reverse and nothing. It does go into drive and the car will move. We put it on jack stands and in reverse the wheels didn't move, they turn in drive but the trans seemed to only shift one time. We dropped the pan to check the low/reverse band adjustment and the actuator piece between the arm and the band had fallen out. I reinstalled thebar and adjusted the band according to a motor manual (72 in/lbs, back off 2 turns and tighten jam nut. Put everything back together and checked again, now the tires turn and still have drive. Put the car on the ground and still know reverse(It sounds like there is an rpm drop but it also feels like its fighting itself to try and move).I bought a rebuild kit and a "trans guy" who is now the invisible man put it together. I would like to try and fix it myself. Any suggestions would be greatly appreciated. The trans is a 727 out of a 69 B-body, it's going into a 72 Swinger with a 383. :banghead: