My trans has a .73 final drive ratio. With 4.10 gears and 42 inch tires this gives me about 77 mph at 1850 rpm. The lower gears are mostly worthless for this application. My calculations show that with a 3.50 rear ratio top speed is 90 mph and at 1250 rpm its 61 mph. 3.00 ratio gets me 105 on the top and 71 mph at 1250 rpm. !00 mph is a little to quick for my liking but 1250 rpm at cruise would be nice. Most of my driving is on the flat but even for pulling the long western hills direct (8th gear 1 to 1 ratio) should work fine. More thoughts on rear gear ratios would be much appreciated. I need to decide befor I start looking for a frame section at my local truck wrecker yards, i plan to buy the section with axle attatched. I will seriously consider the 26 foot box. It would be easier to build it that way than stretch it later.
Thanks guyz.