Very tough. very powerful. This is my first turbo diesel truck, and I am amazed at how strong it pulls. It climbs the steepest hills without losing speed and without shifting out of overdrive. I acheived 20 MPG on my last trip, which is amazing for a truck that's over 5500 lbs and makes 440 lb/ft of torque. All of the 6.5 TD shotcomings you read about were fixed by the time the 2000 rolled out, so I have had NO trouble whatsoever ... never heats up. The 4 speed HD auto is the toughest out there, and the truck drives like a dream. With $1000 in upgrades, this thing will run like a hot rod!
Love this truck. The only flaw that we have found is that it was designed with no baffles in the fuel tank. This allows the fuel to "slosh" around at stops. This has made us wonder what was "wrong" with the truck (because of the noise & the feel with the movement within the tank). We found through several service center checks that this is not a mechanical problem. It has not caused any "problems" now that we know what it is. It does take some getting used to. If you keep the fuel level at about a half tank or above you are less likely to notice the movement within the tank.