5.38 is going to be WAAYYYYYY too low for you with 37s IMO, especially since you have a 4:1 transfer case. I am running 5.13's on my '13 (3.6L) auto on 37" Nitto Trail Grapplers. Even that is pretty low for most people. On the interstate I'm pushing 3000 rpm around 70-75mpg. That is a bit aggressive. I don't have the rubi TC, so I needed to go a bit lower for offroad purposes. Honestly, you'd probably be most happiest with 4.88's and 37s. You could probably live with 5.13s, but considering you have the TC, I'd gear higher for on-road. I average about 13.5 mpg. Just around town the gearing is great. It's just at the high end that the engine will really hum....and there's a huge difference in fuel economy from 65 to 75 to 80.

I used to downshift from 5th to 3rd all the time as you describe, especially in to the wind. I hardly ever have to downshift anymore at all....usually only if I'm gassing it to pass someone. The one thing that is a bit annoying is when traveling to hilly parts (like Colorado or the likes), and I'm using cruise control, it will downshift from 5th to 3rd WAYYY before I think it's necessary. Even if I force it to 5th gear, it will still downshift to 3rd at some point. It just skips right on over 4th all together. What I find is I just refrain from using cruise control in those situations, and/or I manually downshift to 4th before the transmission tries to downshift itself.

**if you went with 5.13s and still weren't happy, you'd really be needing more HP rather than gearing.

 

I agree with you 100%...I'm going to do 5.13's because I'd rather have lower gearing than higher for my type of wheeling in the rocks.

Chris

 

I would gear for your pavement terrain tbh. You are not going to have problems in the rocks regardless of gearing cuz you have that 4:1 TC. You should really be on the fence between 4.88 and 5.13 IMO, and given the TC, I'd lean 4.88. Without the TC (like my situation), have to rely more on the gearing for offroad. Ideally, I'd like to be around 2400-2500rpm on the highway. 3k is too high, but mine is more or less a toy these days. It's a little commuter car for most my miles.