KWIKNVA

That "Rattle" noise in the video by Z06killers sounds to me like the rattle described as the flexplate rattle ( sounds like heat shield rattle) which is common. Hard to be certain as it also sounds like he is driving on a gravel road with the windows down. Clearly to me it isn't a "knock". I'm like kwoodwo. He has almost described my symptoms. My issue is what would cause a knock that actually goes away once the tranny hits 120-130 degrees and the engine is at 200-210?? However, the knock I hear is at 1000-1800 rpms. I can bring the truck to 30-40mph and shift into neutral and rev the motor and no knock at cold temps. I can idle on a cold start in park and no knock. Once in gear and I accelerate the knock is there until the temps come up which takes about 5-10mins. Not piston slap which would go away on avg. 5-60 secs after start up. I listen to a video with a 6.2L with piston slap and it sounded like someone banging a aluminum bat against the block. My knock sound just like the growl of the predator. I've consulted two of my local tranny shops that have been in the business for 25 & 80 plus years and these symptoms didn't jump out at them as something they had seen before. The flexplate rattle is something they said they see often with the 6L80 trannys. So, I'm running out of ideas. Every logical idea seems viable until you throw the fact that the noise goes away when the motor isn't under a load or is at normal running temps. So, if it ain't Flexplate "rattle", "Piston slap", or "lifter tap" I have no SEL, no visible or audible exhaust leaks, no misfires or poor performance. Because the truck runs so good I don't see the need to pay crazy labor cost to have the motor or trans torn down. If I can pin point the the problem then I may throw cash at it. kwoodwo! What was the end result?

My 09 Denali is making the same knock. Sounds like the growl from the predator when driven cold. I can shift into neutral at speed or parked at idle and rev the engine with no knock. Once the tranny hits 120 degrees and the motor is at 205-210 the knock goes away. I've heard piston slap and lifter tick before, slap and tick generally go away in 30-60secs unless extreme cold temps. My knock is there are long as the trans and motor are under 120/210. Is this a tranny issue? pump or converter??? Best way to describe the knock when accelerating is this. http://youtu.be/OQwA14YWdqA Has anyone had this fixed?