I blew an old motor and the camshaft was spun. i ran it for 1600 miles before the cat caught fire. now i have exhaust system and new motor but tranny hesitates bad at low rpms and sometimes theres a build up of pressure and a knock when i let off the gas. please let me know of any ideas

 

Have you checked the fluid level? Could be low and causing the torque converter to act up.

 

the fluids good. good color consistency and filter