What gear ratio for 35s
 

Hello I soon plan on adding a set of atx cornice haven't decided between 17s or 18s, leaning towards 17s and wrapping them in 35 inch toyo open country mts. I have a 2010 Jeep wrangler unlimited sport and was wondering if I need to re gear. A guy from local jeep club says I will need to and said to go to 4.88s. And while trying to research have seen a lot of people running 5.13s and say that is best if ever decide to go to 37s. I'm new to jeeps so woundering what is best to use brands and ratios. also any other tips. Like will I need a programmer for speedo. Thanks for help

also its an auto with 3.8l engine if that makes a difference. Another thing is it worth putting lockers on it while I'm at it and what is best to get thanks

5.13 if you have an auto and 3.8L. Don't go higher (numerically lower).

You will save money if you do lockers at the same time, but I would not spend any money on D30, because once it fails, you will need to get a new locker for a 44 axle. You will also want to consider upgrading axle shafts in that case. You could lock the rear and replace the shafts. An ARB works great, but there are other selectable options as well.

And yes, you will need a programmer for speedo if you change the tire size. Doesn't matter for a gear change though.

My suggestion get the tires you want, drive it for some time, then decide if you want anything more.

I did G2 5.13's gears and Trutrac's front/rear. I put Nitro sleeves, gussets and lower control arm skid for extra $100, on the D30. Yes, the front gears are small. But, with trutrac's, air down tires you can go easy on skinny pedal. If and when it breaks, will upgrade from there. So far it holding up fine!

Drive it with the 35's and decide for yourself. (yes, you will want to regear, but 'you' need to decide that, not us...)

What gears do you have now?

Stuck to the top of this Modified area are some FAQ's. In them, you will find some JK specific gearing charts broken down by engine and transmission. Plug in your current gear ratio and see what you think.

When you have the tires on, one thing you can do is just turn the OD off. This forces the transmission to not use overdrive. Once you have the rpm number for 35's from that chart (use measured tire height, not mfg spec), just divide it by .69 to find what your rpm's will be with OD Off.

For instance, with 3.73 and 35's that measure 34", the chart shows you would be at
1781 rpm @ 70 mph (OD On)
1781 / .69 = 2581 rpm (OD Off)
And 5.13's = 2450 rpm (OD On)

Doesn't help at all around town, but od/off will get you a good feel for what your rpm's will be with new gears.

Yes, you will want a programmer or tuner to set the tire size and gear ratio. Helps with the shift points on the auto's.

If you currently have 3.21's, you will need a new open carrier for the front d30. Should be around $90. Or, if you decide on traction, any of the full case limiteds/lockers will take the place of the new open carrier.

Whether or not to install lockers is a judgement call. When the axles are ripped apart is definitely a good time to do it, but, do you need them? Is the extra traction worth the cost to you? Do you want to throw money at a d30? Do you have any plans of upgrading axles in the future? (you will see a lot of different comments on both sides of this argument, read them all and decide what is right for you...)

People have favorites, but brand doesn't seem to matter much for gears. With a few exceptions, most of the 'JK' gears still seem to be coming out of the same place in asia. Use whatever your installer suggests, or look at price and warranty.

I run 4.88 with my 3.8L. It is my DD and I drive 30miles to work (60-70miles a day), the 4.88 kept me close to stock 4.10's and kept my MPG decent. I've run overland trail with guys that have 5.13's and at the end of the day I always have and extra 60-100 miles left in my tank compared to them.
I would say if the Jeep is not a DD or your commute is short then go 5.13 otherwise 4.88
either one is a huge improvement over stock gears running 35's

Drive it with just the 35s for a while - and I mean months, not weeks. It won't do any damage and you'll get a feel of what you really "need". You might be surprised. I drove my 3.6l on 35s with 3.21s for a couple years. I ultimately went with 4.88s because that's what was in the axles that I swapped in. Had I had to do it from scratch, I would have gone 4.56. But now I am thinking I might go with the 37s at some point, so for the 3.6l, 4.88s are idea.

For the 3.8l, I understand that 5.13 and 37s are a good match.