rhagfo wrote:
One other thing, with a diesel, you don't need to slip the clutch, don't "dump it", but you don't need to rev before releasing quickly. Drive the truck through town a while to get use to the feeling.
This is spot on. You mentioned that you have never towed heavy with a manual. A key difference between your friend's truck and, say my VW Passat, is that the truck launches with zero throttle. You choose the appropriate gear (usually the lowest with that trailer) and smoothly let the clutch out to take off, gently rolling on the throttle as the clutch becomes fully engaged. It seems counterintuitive to drive this way, but it works even when launching on a hill.