When in neutral, there is no noise. However when it is put into any gear, I hear a weird knock that sounds a lot like a rod knock, but it isn't. It sometimes also sounds like a heat shield rattling, but a lot louder. Is this probably the converter? If it was the flexplate it would do it no matter if it was in or out of drive right? And lastly, could it be the direct drum bearings?

 

could very well be the flexplate.... they`ll crack around all the bolts and only "knock" in gear from what I remember

 

on my 700r4 in my truck. i had a broken flexplate and that thing made the worst rod knock noise i ever heard. if you really rev it up you should hear it. I broke 2 of them and then i called summit and bought a good one. cost like 80 bux or 100 i can't remeber but i haven't broke one since.

 

Also might be a bad tq converter. I had an engine (I thought) that would knock every time I got to 3k. Replaced the engine same thing, turned out the tq converter was causing the noise all along. I felt stupid, T5 cured the problem.

 

Yeah, Chevy trucks are notorious for cracking flexplates. Look at the bracing on a 4X4 sometime. Obviously the factory knew that these things had a hell of a lot of torque running through them, especially in low gear. There are two struts from the engine mounts to the trans shield, which is cast aluminum rather than platic as on most cars. There is a long strut from the t-case to the bellhousing.

Whenever I reaplce and engine I just buy an SFI flexplate as a matter of course. They are relatively cheap, and the hassle of having to remove the trans makes them well worth it. I've never cracked the one on my K5, even with 38.5" tires, 4.88s, a 2,400 stall converter, and a 360HP 420lbsft. 350. It rarely gets driven gently either...