Diesel enthusiasts love a lot of things about oil-burning behemoths like 2001 Duramax trucks. Locomotive torque and fuel economy are usually cited as the best things about big diesels. But there's another side to those who love these road-going juggernauts -- the love of outright, unstoppable speed.
In stock form, the 300-horse LB7 Duramax truck is gearing-limited, at least in the sense that the computer will stop fueling the engine at anything past 3,250 rpm. Depending on the transmission you have, you'll run out of rpm between 107 and 110 mph. Five-speed trucks are on the lower end, and six-speed trucks on the higher-end. However, that isn't the end of the story, because an LB7 will spin to 4,500 rpm without exploding anything. And the power potential to hit that rpm in top gear is very nearly there with with little more than an air filter, an exhaust system and a power tuner. At 4,500 on the stock-sized tires, theoretical top speed comes in at a staggering 151 mph. Theoretically, you could add 15 to 20 mph stepping up to taller tires, but you'd run out of aero-limited power before you got there. In the real world, many enthusiasts with basic mods and stock-sized tires report a sustained 140 mph or more for miles on end without excess exhaust gas temperatures or blowing anything up.