Chevrolet Repair: knocking noise coming from rear of engine, merchant seamen, torque converter

Question
Hello van Iam back, Iam a merchant seamen and just got back home,my 90 silverado has been parked awhile,but today i took the plug wires off one by one while the engine was running and i still have the knocking noise.Tomorrow iAM GOING to check the flex plate to see if it is cracked.

Answer
Yep...check for a crack. But also check the bolts mounting the torque converter, to make sure they aren't loose.
While in the area, pry the crankshaft toward the front, and then toward the rear, to see if the main bearing thrust surfaces are worn out. I have had the crankshaft main jurnal wear out there, and allow the shaft to move too much.

Van