Not sure if to post in 2nd gen or first gen.

I have a 96 dodge 3500 4x4 auto and I put a 1st gen motor in the truck and it's all put together
When it turns over there 8 a pound knocking sound comeing from the granny area
I pulled it apart and checked all the bolts on the fly wheel and they are tight
Now with the torque converter Un bolted from the fly wheel it doesn't make the sound.

Any help will be much appreciated