It is interesting, entertaining, and in some cases frustrating how much you learn after having completed a build. I put 4.56 gears in the truck because I had them and everyone seems to think it is a good ratio for off road crawling. However, given 35" tires and the gear ratios in a NV4500 transmission, I have to tow in 5th gear if I want to drive highway speeds. Clearly, it is best to tow in 4th gear (1:1). In addition, the 4.56 gears mean that my driveshaft is spinning at 3,500 rpm at 80mph.
Currently, my crawl ratio is 5.61x3.0x4.56 = 77. I think 80 or so is good for what I do with the truck.
The truck sits at about 2,600 rpm at 80 mph on the freeway in 5th gear, which would make a decent target rpm for towing in 4th gear. So, if I want 2,600 rpm in 4th gear, I need 3.42 gears. I'll be likely saving fuel when not towing since I will be at 1,950 rpm in 5th at 80 mph.
However, my crawl ratio will be reduced to 5.61x3.0x3.42 = 58. If I swap gearing in the transfer case from 3.0 to 4.3, I'll then have a crawl ratio of 5.61x4.3x3.42 = 83. A nice feature of having an Atlas transfer case is the fact that you can tune your reduction gear ratio to what you need and use the road gears that make the most sense for what you do with the vehicle.
The calculations are in the attached file if anyone is bored enough to look.
Currently, my crawl ratio is 5.61x3.0x4.56 = 77. I think 80 or so is good for what I do with the truck.
The truck sits at about 2,600 rpm at 80 mph on the freeway in 5th gear, which would make a decent target rpm for towing in 4th gear. So, if I want 2,600 rpm in 4th gear, I need 3.42 gears. I'll be likely saving fuel when not towing since I will be at 1,950 rpm in 5th at 80 mph.
However, my crawl ratio will be reduced to 5.61x3.0x3.42 = 58. If I swap gearing in the transfer case from 3.0 to 4.3, I'll then have a crawl ratio of 5.61x4.3x3.42 = 83. A nice feature of having an Atlas transfer case is the fact that you can tune your reduction gear ratio to what you need and use the road gears that make the most sense for what you do with the vehicle.
The calculations are in the attached file if anyone is bored enough to look.