Originally Posted by alexrex20
I drove mine home about 90mi, all highway, and it did OK cruising at 60-65mph. I guess mine may not be geared too low, because it did 65mph at a safe 2800rpm. My plans are to swap in my EFI 496 and a 6-speed Allison, so it should be even more highway-friendly.

My gearing is fine; I thought the issue was with the 2spd being less reliable or something... smile

I will be using this truck to haul my 36ft enclosed racecar trailer, or potentially a 46ft GN racecar trailer. My buddy pulls a 48ft GN flatbed hauler with his F450, and we "car pool" our rock buggies 3x or 4x at a time on it. I suspect I may be volunteered as the rig hauler on the next trip. lol
With a 6 speed (double overdrive) you probably want a lower geared rear axle than you have now if you plan to tow that much weight. Or have it programed back down to a 5 speed?
Sounds like an interesting project and truck.

Run some numbers and ratios in a gear calculator and see what you find.
http://www.onlineconversion.com/bigger_tires.htm

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-