Don’t assume that 4.88 automatically means worse MPG than 4.56. Many of us here, myself included, have had better mpg from the numerically higher ratio.IMO,
NSG370/29.5"/3.73 = 2498rpm @ 70mph (over 400rpm higher than the 42rle)
Represents the best "stock" (ratio wise) to which I am trying to return, not the
42rle / 29.5" /3.73 = 2052rpm @ 70mph
Which is represents garbage RPM even in the stock form.
I have driven TJ 4.0 with 6 speed a lot in past, and it was best combination of highway RPM, power etc.
With our tire combo, 4.88 will provide more power, but more fuel consumption, which is much better for hilly terrain, and 4.56 will be a better choice for flat as a tile place.
So my conclusion is that for gear ratio, one needs to look at engine, transmission, tires (real tire size, not the advertised ones), tire pressure expected on highway (size changes with pressure), and the terrain for which one plans to optimize the gearing.
I would not want to regear to a ratio that puts me at 2500 at 70. I want to be more around 2800 at 70 if possible and 3000 at 75.