What kind of trans? My first car I had I put a driveshaft in it that was too long
ops: it had a th 400 and it busted the center support in the case and pushed everything fwd into the back of the crank. I only had that driveshaft in there long enough to drive it out of the garage a time or two til I got the right one..trans started to slip a little and when I went to remove it I found the sloppy thrust in the crank.
Also if the converter has balooned it will push fwd on it.
cheap converter + lots of power braking can do that...so I'm told.