87 chevy tranny help

[chevy_power1995]

I blew up my transmission im my 1987 silverado and i swapped it out
with a different transmission and torque converter. and it moves fine
and everything but theres a LOUD knocking coming from the flywheel/
bellhousing/area i dont know what the hell it is any suggestions????
and it has fluid in it and the torque converter bolts are really tight
and i didnt remove the flywheel so its not that and i also inspected
the flywheel for cracks any one know whats going on???