I have a 73 J4000 with a TH400 and QT. It slams into gear going from P to R, then slips and shudders going into D. Once in gear, it shifts fine. I'm thinking it's a torque converter problem. Any suggestions?
Shuddering on older transmissions is usually due to worn clutches and bands. You are probably due for a tranny re-build.
Newer trannys with lock up type torque converters also have shuddering problems when the friction material in the torque converter is worn out, but your TH 400 doesn't have a lock up type converter. This is a pretty comon problem for early '90s Fords with E4OD trannys.