mistasparkl

I don't mind the 2700 rpm @ 70...the gearing is just a taaaaad low for extended highway, but its better than sluggishness, especially after a bunch of extra weight is added (bumpers, winch, armor, etc). However, if you're that worried about it, it's an easy fix--just the excuse to get some 37's

JPB

So how would 37's run with 4.56 (auto)?????

RPM's on highway (higher or lower)?

MPG (Higher or lower)??

Sluggishness???? or not too bad?

planman

All I can say is don't fear the gear.

The difference between 4.56s and 4.88s at highway speeds is less than 200 rpm for a '12+. Running a slightly higher rpm to produce more power to turn larger, heavier tire/wheel combinations makes sense. The last thing you want to do is run stock rpm levels with larger, heavier tire/wheel combinations.

Unless you spend most of your miles at 80+ mph, go with the lower gear (higher numerical value) to regain lost performance.

There is a reason that Ram HD trucks with 4.10 gears have higher towing ratings than with 3.73 gears. Yet the mpg economy results unloaded are almost identical.

Have you guys read the FAQ stickied thread?

The bottom of post #4 covers this topic and has spreadsheet graphics that show rpm by actual tire size, engine model, and transmission type:

https://www.jk-forum.com/forums/modified-jk-tech-2/modified-tech-faq-answers-questions-every-newbie-has-18617/


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omjee

I'm running 4.56 gears on my 2013 with 35's. Definitely recommend it!