With the different gearing on the '12s, 5.13s would be too low for anything much below a 40 inch tire. If you do the math, you can go a size or two higher on gears with the '12s and be good.
For instance, 35s with either tranny would be decent with 4.10s and geared fairly low with 4.56s turning aroundd 2700 rpm at 70 mps. 4.88s and 35s are turning a tick over 2900 at 70 on my '12 with an auto.
Honestly, I kind of wish I wouldn't have gone so low on mine. I have plans to go to 37s, but am on 35s now as I took the tires and wheels off my '09 that I traded in. I also pull trailers and even pull an teardrop offroad on occasion so wanted the lower gearing. However, with the power of the 3.6, 4.56s would have most likely been plenty of power even with the 37s and given better highway manners. Also, the first gear on the auto is much lower than the old 4 speed which also really helps with higher gears.
This has me curious though. My '09 Rubi with the 4:1 t case and my '12 with the 2.72: tcase feel from my butt-meter to have very similar crawl ratios. I'm going to have to figure out the math...
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