So long story short, I blew up my transmission then swapped it. Now the starter is starting very slow for the first week. Now when i started it this morning it revd up to 3000rpms and stayed there till I turned the truck off. After 20mins it overheated and force shutdowned. Anyone know either issue or how to fix
EDIT- it is a 4L60e

 

a slow crank right after a trans swap usually means you forgot to tighten the main ground strap connecting the engine to the chassis that crazy high idle is almost certainly a massive vacuum leak like the brake booster hose getting knocked loose when you tilted the engine the overheating is likely from it running super lean from the vacuum leak or you pinched a wiring harness between the block and bellhousing