redjeepjk12

the other day i found a chart that shows u the best gears to tires size for auto and manual tranny and where u get most power and best mpg. please post it up if you know what im talking about thanks

chknkatsu

2vpblaze

So just out of curiosity, I am wondering how exactly this chart works. I have a 3 in lift woth 33inch tires and I am doing terrible with my rpm. I have stock sahara gears. Correct me if I am wrong. If I were to upgrade tp 4.88 gears I would be getting the same rpm that I am getting now with my stock sahara gears.
Just looking at getting some clarity on this. Thanks for the help

jeepmedic

You need to get a build sheet from the dealer and find out if you have 3.73 or 4.10 gears currently...then figure out the new gears. 4.88s would prob be a good choice. If you are looking to ever going to 35's then most folks with an AUTO go up to 5.13s. I know I did and it was the best choice ever.

This link may be helpful too. It is an excellent write up.

https://www.jk-forum.com/forums/show...?82262-Gearing

nthinuf

There is a big FAQ's area stickied right to the top of this modified area. Lots of good info there, including the rpm charts...


It's a simple cross-reference. Figure out what gears you have now, go measure your tires (measured, not mfg's spec), then cross reference.
A bit of advice - You have a 4door auto. Skip the 4.88's and go straight to 5.13's. (and if you happen to swap in a front 44, skip the 5.13's and go straight to 5.38's... )

Stoneaxe

Keep in mind the tire size noted on the charts is actual not reported. Take a tape measure out and measure your tire height.

rickster

So, from the chart I see that a 3.73 with stock tires (32")and auto tranny is not correctly geared from factory? That combination only puts me in the yellow part of the chart.

Grognard

That's true. I am in the same boat - I am planning to upgrade to 5.13s when I do my lift and 33s in January.

Read the FAQ at the top of this section

https://www.jk-forum.com/forums/show...ery-Newbie-Has

Lot of good info there.

rickster

I would re-gear also, I have a 2.5 BB, and planning on 33's. However, a regear will surely void my life long drivetrain warranty.

Grognard

Talk to your dealer and make sure. My dealer will keep my warranty if they do the work - I have a lifetime on my 2010 too, but its not through Chrysler.

My dealer is also competitive on costs for installs. But, if given a choice between the lifetime and installing prorock axles, well, I have already started saving