Chevrolet Repair: knocking sound in bottom of engine, torque converter, flex plate

Question
i have a 1990 chevy silveradoz71,when i start it up ihear a knocking noise coming from the bottom part of the engine towards the transmission,but when i give it a little gas it stops,the oil pressure is not dropping and you only hear this sound at idle what could it be?

Answer
Hello Earl,
I have seen that noise from a cracked flex plate where the torque converter bolts on.
I have also see it when the thrust bearing on the crankshaft was worn out, allowing the crankshaft to move foreward and backward. Check that by using a large screwdriver or bar, and prying the crankshaft toward the front and then rear.

obviously there is also the knocking rod possibility.

And a broken crankshaft can do it...and still be running ok.

Van