I have an 01 Neon with an automatic transmission. The bolts holding the torque converter to the flywheel came loose so I've had to pull the transmission and replace the flywheel and torque converter. The problem I'm having is this: with the torque converter in place and bolted to the flywheel, I cannot rotate the engine by turning the crankshaft pulley unless I leave the transmission to engine bolts loose. When the bolts are loose, the engine will rotate really easy. But when I tighten the bolts, everything locks up and will not rotate. Yes, I have the spark plugs out and I have the flywheel facing the proper direction (ring gear welds facing toward the transmission and the little flex plate with the lip is on the transmission side of the flywheel). Other than not having the torque converter pushed into the transmission as far as it should go, could anything else be binding?

 

I think you nailed it. Sounds like the notches in the torque converter didn't engage the tangs in the pump. In other words the torque converter isn't all the way in.