Mine does it as well. I've ridden in 2 other trucks that also do it, and both of them had been built by professional shops. I've found that the 02+ OS in the TCM does it pretty bad, but I rarely ever get it with the 01 OS. Roll the windows up and you don't hear it either. I only hear it in mine with the windows down and driving in an area where sound can echo out from undeneath the truck and teh trans temp is in the 120-150 degree range. Also I found that the 680RPM idle speed made it less noticeable than my current 600. I've evn heard it in a 6 speed with just a JR in it. I just chocked it up to the nature of teh beast. Sort of like how my C2 doesn't prefill, along with another 01 with a built trans I rode in didn't.
