Says the one who claims to know MORE than the jeep engineers and have more resources available to him than them. Fuzzy math using the wrong numbers will do that to you. https://www.jk-forum.com/forums/show...3-gears/page12

There are others who have agreed with me on this subject and have posted such but don't waste their time on here like I do trying to help others out. Like you have said, it's not a one size fits all.

 

By too low I am referring to a higher number. IE, I went with the 5.13s that the "experts" suggested and would have been better off with 4.88s. This still has your motor turning faster than stock to compensate for the added weight and rolling resistance of larger tires. I am not the only one who has said this though I am the one that says it the most.

 

Let me know when Chrysler starts rolling JKs off the line with 35s and 37s.

 

So you think you would be better off spinning only about 200 more RPMs than my 2010 six speed with 33s does in 6th gear? I have stopped using 6th gear altogether, and 200 more RPMs would not be enough to make it useful again. Why would that be where you want your OD to put you? You'd be downshifting all the time.

Christ man, even your 5.13s don't get you to the RPMs put out by a pre-2012 six speed Rubi on stock tires--you're still 300 RPMs shy of that benchmark at 70 mph. You'd need 5.86s just to get there. And that's a STOCK number that Chrysler itself found acceptable.

I read through the thread you linked and it's clear this has been argued to death and there's no convincing either side, so I'm not going to restart it. But knowing your deference to Chrysler, consider that the stock auto pre-2012 Rubis spun 2080 RPMs at 70 mph, and the stock manual pre-2012 Rubis spun 2533 RPMs at 70 mph. Those are Chrysler's flagship Wranglers.

Your 5.13s put you at 2251, more or less in the middle, whereas 4.88s would have put you at 2141, basically replicating the stock auto. So your 5.13s basically "split the difference" that Chrysler found acceptable between the manuals and the autos--sounds like you should find that just about perfect. I can't believe you really think you would have been better going with 37" tires and then just replicating the stock auto trans RPM level that plagued these forums for years with posts about "underpowered" Wranglers.

Of course, either 4.88s or 5.13s on a pre-2012 auto will be a big improvement over the stock 3.73s for 37" tires. But at the end of the day, I think you're just dissatisfied with the 3.8. Gears and RPMs can only to so much for power and you can only squeeze so many mpgs out of a particular engine. You're looking for power and fuel economy while rolling 37" tires on a 4k pound lifted vehicle that's shaped like a dishwasher--there aren't any Yukons you can cram into those differentials that will make it pull like a Hemi with the mpgs of a Prius.

 

So I have a ?. I plan on getting 35s but will move on to 37s later so i would lk to know what gears would be best. It's a 2012 jkur auto. mainly used for mudding and beach. Not really a dd or a high speed jeep.so gas mpg doesn't matter to me. Let me know.

 

I would say start with the stock gearing and go from there. The new 5 speed auto is a lot better with the stock 3.73's. The chart does say 4.56 would be ideal for both sizes. Plan on spending 750 for the 4.56's. They are uncommon therefore the most costly.