Light Engine knock

[gmtech99]

Ok guys, got a question for you..I have an 02 and it had a int light knocking noise that I thought was coming from the loose water pump that I but after replacing that the noise is still there..sounds like its coming from underneath by the torque converter or that area of the oil pan....don't think its coming from balancer....are the flexplates known to crack on these? only does it at idle..as soon as you come off idle the noise is gone....any help would be appreciated