[JM2007QC]

well, I have an 07 3.7 with the 6 speed,. I have noticed a rumble noise too. It seems to only happen when the truck is at normal temps and as you said under load. This can be done easily by leaving it in 6th gear and accelerating slowly when the truck is cruising around 1500 - 2000 rpms. Its sounds like its coming from the back of the engine or maybe the exhaust manifold. I cant pinpoint it but I can recreate it, I am waiting to see if it gets worse but as you said,.. they may say its normal.