Reverse would be nice!

I have a '75 L-48 with a 3 speed auto. When I tried to move it this morning to my surprise I had no reverse, but more interestingly the car would move in L1, L2, and 3 and also in Neutral. In park it wants to jump forward also. I checked the linkage under the car and to the best of my knowledge the tranny is in-sync with the selector. I also checked the vacuum line into the tranny and its all plugged in no sign of leaks, plenty of vacuum. I test dove it and it shifts propperly in 1,2,3 and moves forward in N but not with much force. PLEASE HELP. Steve T.