Bought a 05 auto for $300. Ran and drove. Had hard shift. Cool valve body is bad no big deal. Done trans replacements before so no big deal.( car had new motor, trans had 200k) sourced out a trans from the depot. It's a one plug trans. Ripped out the old one stabbed the new one in. Now with motor and trans mated together the engine will not rotate (by hand or starter) figured starter was bound up on flex plate I removed starter. Still not rotating. Took trans back out. Made sure tq was seated. Went over everything. Stabbed it back in still no luck. Motor rotates by hand with trans out. Installed drive shaft on to tail of trans and input shaft rotates. I'm stumped.... 🤔. 300 dollar car. But don't wana keep throwing money at it. Any pointers. Ideas.. something I'm missing ???!

 

Same torque converter? You sure it was all aligned properly? You should be able to fully seat the transmission up to the engine by hand, if you have to use the bolts to squeeze it together something is wrong.

My guess is either seized torque converter, or assembly is pinching the TQ because it's not getting aligned properly when installing the tranny.

 

Tq wasn't seated properly. It was enough to sammich the block and trans together but not enough to allow rotation. Everything is good as far as I know. I took tq off. Seated it in the trans then bolted trans up to block. Car runs great now.