[Alan Roehrich]

Dwight, I got 8-9 towing a very high profile 28' enclosed camper that had probably 2,000 pounds of extra weight in the trailer and close to 1,000 pounds extra in the bed, and three people in the truck, much of that trip was into the wind, and I was running 70 MPH, uphill and down. Truck pulled it and handled it with ease. This was before I upgraded to 19.5" wheels and tires, and better brakes.

There is more power and more fuel efficiency to be had from the truck. I have a friend with a chassis dyno and various EFI tuning software. I've been pressed for time, so this is moving slow, but I'm going to do some stuff and document each change as it happens. Since I'm keeping this truck, I'm going to go fairly far to see what can be done with it. I think over all there is 100HP and 100 ft/lbs to be had, and I think that if you do not use the power to show off how fast you are, the changes will result in better fuel efficiency, especially when towing. I know what some other guys are seeing with some work in the right places.

I think the single biggest problem is that the power band of the engine is too narrow, it runs out of power and useful RPM for the gearing it has. The one complaint I have is that it downshifts too early, and then runs out of useful RPM before it will upshift, so it has a hard time getting to that next shift to drop the RPM back down. So my goal is to increase the power available so it downshifts less, and spends less time in the lower gear. Using too much throttle and turning too many RPM is where the fuel goes.

I wish this truck was a 2006, as the 2006 has a 6 speed Allison. It's not a conversion that can be done easily and affordably, I doubt I will ever do it. I got a sweet deal on a one owner low mileage truck, so I settled for a 2003. A 2006 is a better truck to start with, but they 8.1L trucks get harder to find every day, especially the newer trucks, as the Duramax got more popular, and GM was intentionally killing the big block. I think it might be possible to make a 3.73:1 gear work well with the 6 speed, but I'm not sure it is a good idea with the 5 speed, my truck is a 5 speed with a 4.10:1 gear. I swapped to 19.5" Vision aluminum wheels and Hankook tires, which made a big difference everywhere, I think the RPM drop was worth at least 1 MPG.

A new truck like mine would be $70K, if you could buy it. I don't mind spending $2K or $3K on this one. It's still under 100K miles, and as Bridges says "that truck will go well over 200K miles, and when the time comes, we'll just make it better for the next 300K miles".