the trans gearing isn't entirely relevant nor is the RPM range. simply moving to diesel and rpm is automatically way to high. And engines have optimal points at different rpm based off their design. So simply walking in and saying you want 1800 rpm in 8th at 70mph and selecting a final drive to match won't work. the 3.6 doesn't make enough torque to do that. But a 6.4 Hemi would. So in the case of this generic list, it just a generic point for all road trucks as there are more cases than 8 speed auto Jeep Gladiators. everything has a 1:1 gear and usually 65mph capable. So thats the frame of reference albeit broad. But its designed to cover everything gas powered from Honda Accty to F250 Tremor gasser. So with our use case, we could say 5.13 is too high for 37s due too having an 8 speed. And if you went custom and got a hemi swap that would make it even more so. But if you had a manual gladiator, then that 5.13 make a bit more sense. But because there is that big of gap between a single model of truck. I got the list above as broad as possible as not to favor any particular variation. Its a ballpark, and a rough one, but close enough to help visualize the point im trying to get across.
That's precisely my point. These 3.6s make nothing usable below 2000rpm and the second stage of the oil pump kicks in at a tick under 3000rpm. So at highway speed you have no more than 1000rpm window to operate with. So you gear in top gear for the highway speed and load you plan on running. If you routinely drive 90mph for hours on end, gear for that. If you never hit 70, gear for that.
100% correct. Mine is a manual and I hit the second stage of the oil pump at 85. There are a few highways near me where that is the speed limit, so I camp in the slow lane with the cruise on.
7th with 4.10s is almost identical to 5.13s in 8th...but under low loads I still have the nice low rpms of 8th with 4.10s and the deep geared guy doesn't. 7th is still an overdrive and equal to the top gear in a JK with an auto. I don't want to be in 8th all the time personally. I'm my opinion that's not the purpose of a transmission with 8 speeds and 2 overdrives. In reality this trans had such a huge spread you can get away with almost any gearing. Even factory you can get everything from a JL sport on 32s with 3.45s to an XR with 4 56s and 35s to a Rubicon or mojave with 4.10s and 33s further proving my point. 3.45s and 32s is equivalent to 4.10s and 37s ie my mojave drives, shifts, etc like a stock sport. Our JLUR with the xr package felt over geared in the stock 35s at freeway speed. Not overly so but not optimal. Our 4.7 1st gear makes 4.10s equivalent to a JK with 5.41s. Nobody ran deeper gears than that on a JK on 37s and yet everyone thinks the JL/JT needs more gearing for 37s. It flat does not.
All of those things are correct. And you are one of those guys that seems to be ok with running in 7th gear as needed. Some people it drives crazy..
Mine is a manual, so different animal. All the autos that I wheel with are rubicons, so never apples to apples.
