I have an 01 6-speed with a Smarty, Quadzilla Adrenaline, Valair single disk, 285 tires, dually with 3.54. With my clutch I cannot slip the clutch out at all. It's either in or out. I have tried 4th low and just cant hold the gear, it draws the truck right down to almost 1500 rpms. I bring up the RPMs to about 3200 let the clutch out and peddle it from there depending on how the truck is hooking. I have Master Craft tires that hook great. Plus a 1000 pounds in the box.
It takes a bit to learn how to drive one!