Anybody good with a 727?

OK...so i head back home open the shop to take the Dart for a spin...I run it around the block and notice the tranny is sticking a little,so i head back to the shop turn around put it in reverse and hit the gas...i feel tenion but no matter how much throttle i give it wont move...So i pop the hood add a little tranny fluid.(just to level it up)Nothing changes so i pull it into the shop put in park let off the brake and i can feel the car pulling forward like its steel trying to stay in drive...When i rev it up,you can tell there is tention on the motor.If anyone has had this problem or knows what it might be i would appreciate the help....thanks