The torque tube is supposed to slide, and sometimes it can have a groove worn in it or just be bound up tight. I fought this problem too and ended up loosening up the seal, clamping the bell to the crossmember with some wood blocks and clamps, and bouncing up and down in the bed until it loosened up, then I got the play I needed to tighten it down.
The other way to do it would be to loosen the transmission bolts, slide the tranny back to meet the torque tube, attach it, then tighten them back up.
