Thinking of regearing my JK... 09 X Unlimited, auto, 3:73 gears. Just got 2.5" TF BB with shocks, new wheels and 33's. I'm thinking about getting the Superchips programmer next week. From what I'm hearing besides resetting my speedo and shift points, it should give me a little more UMPH!!! something like 18 hp and a little more torqe. If that doesen't do it for me then I'll regear. This is my DD. I live in SoCal. So I'll be looking for a good shop to do the regearing. Does anyone know of one in the San Bernardino / Riverside, CA. area. I live in the mountains at about 6500 ft. I drive up and down the mountain 4 days a week to go to work down at sea level. So half of my daily driving is mountain driving and half is interstate driving. I'm thinking either 4:56 or 4:88. What do you guys think?

Thanks.

 

If that were my situation, I'd go with 4.88's. Sounds like lots of up/down driving and not much higher speeds, and gives you the option of moving to a taller tire without the need to regear again. (actually, I'd go to a 5.13, since I am biased and I think the auto's are way underpowered from the factory) Anyway, give the programmer a shot and tell us what you think of it...

 

With my stock set up my mountain speeds usually average about 45mph to 60mph going up the mountain. I have the OD off going up and down the mountain. I could go a lot faster up the mountain and have, but the roads are pretty winding and I'm not usually in a big hurry to get anywhere real fast. I'm pretty much in 3rd gear all the way up unless I put my foot in it to get around somebody going slower than me

Interstate driving is pretty much between 65 and 75mph. That's my driving style. I put my foot in it every once in a while and open it up.

I just got all my mods finally done today and haven't driven up the mountain yet. I hit the Interstate first for about 20 miles, then the mountain for about 25 or so. I guess I'll find out how bad the shift points are off when I take off for home.

 

stick 4.56
auto 4.88

 

I am sure I am in the minority here but I would go 5.13. At the very least I would go 4.88. You will get tired of 33s and want more meat... If you gear for those 33s you will have 4.56s. 4.56 and 35s or 37s or whatever will suck. If you go 4.88 or 5.13 your milage will be poop but your power will be great. The jeep will get in OD fast and stay there. Plus if you go offroad you can put the shifter in 1 and have a nice creep.

4.88 may be a good choice for you. 4.88 with 35s is close to stock. It wouldn't be too horible low with 33s either. Good luck. Lets see this thing.

 

5.13s and 33s is gonna be screamin

 

Seer1 ran that combo until he got 35's and really liked the power and the way it drove. You'd be turning 2700 at 75 mph on the freeway. I think that is about ideal. Same gears with 35's you'd be at 2600. That is what I have now and if I has my druthers I'd rather be at 2700-2750. If I were gearing an automatic for 35's today I'd probably go 5.38's (they weren't available when I regeared). If, or when, I go to D60's I'll probably go with 5.38's.

Don't fall into the 1960's and 70's mind set that lower rpm means better fuel economy. With this heavy brick and it's marginal engine it gets better economy if you let it rev and not lug. Just keep it under 3000 or your fuel economy will suffer. Why does this work out? The dyno charts show the max torque output of a stock JK at 2600-2900 rpm and it's putting out about 20-25 more HP at those rpms than say a stock Rubi JK (32/4.10) spinning at 2250. The OD now becomes useful and the cruise control actually works; even in Colorado.

GEARS GEARS GEARS! In comparison most most everything else is pissing your money away until you regear.

A caveat - this mainly applies to automatics. The .69 OD of the automatic changes a lot of things in comparison to the sticks .84 OD. Which is not to say that sticks don't benefit from regearing; but they don't have to go so deep.

 

As a happy owner of the Superchips Flashpaq, it's not going to fix the drivability the same as a set of gears, especially with how under-geared the automatics are. Moving from 3.73s to 4.56s is going to get you into the power band 20% quicker and with the Superchips, you may pull somewhere between 8-10% more power. That leaves you with a deficit in the feel of your vehicle and the power it puts to the ground.

You are also on the fringe of where you can maintain highway speeds for grades, hills or passing. In essence, OD is now of nominal use with even the small jump in tire size (weight and distance traveled per revolution). 4.56s likely get you where you want to go but leave no room. No room for added weight in the future, larger tires, bumpers, skids or any of the other stuff that can increase someones ride by a half ton. That said, 4.88s are probably the right way to roll and the Superchips is good enough to split the difference from 4.56 to 4.88s or 4.88s to 5.13s if you decide to roll on 35s at a later date.

Also, the mention of the difference between a 6 speed and auto was understated. There is a good 20% difference in final driveline ratio coming out of the manual transmission gear box as compared to the automatic.

 

As I don't think my better half is going to tolerate me getting a Hemi until she gts her kitchen remodeled I'm probably going to give the Superchip Flashpaq a try. With the 5.13's it may just be a nice combination for an auto.

 

Gears? Now here's a topic that hasn't been discussed in a while. If you really want to know about something as serious as ripping the differentials apart ask someone who has really been there. At 6500 feet you need all you can get. Throw in some gear or passengers and your Jeep will bless you for getting 5.13's. I'm not talking about some ridiculous table I found on some site or another I was living it. Screaming? Hope you meant screaming as in, "Wow! I didn't know the JK had it in him!" And not, "Shit! The Jeep hasn't dropped below 5000 rpm since I started it up!" The OD loves 5.13's and 33's. The 35's I put on it turned it back to normal.

Here's a post from yet another thread on this:

Quote:
Originally Posted by RedneckJeep View Post
Interesting. Could you stand the 33s and 5.13 permanently? What's your RPM at 60?
Great question Red. I think I would go 5.13's if I were still running stock Rubi's. Before I post the numbers let me tell you what's rolling here:

First of all put away your calculators and some table you found posted somewhere on the I-net. I'm gonna tell you what is, not what's supposed to be. If you want to call me a liar then come out here and do it to my face. Then we can go on to important stuff like rolling over your calculator a couple of times and getting on to wheeling some great trails.

Now this used to be an '07 Sahara Unlimited with an AT. Stuff that may effect the numbers include full RH skids, full doors, hardtop, Shrockworks sliders, Nates 4x4 full width bumper, 9500ti winch, Currie (massive) control arms F&R, diff armor, chromoly axles F&R, wheel spacers, Tuffy everything, RH rear bumper/tire carrier, j-can carriers, at anytime about 50 lbs (minimum) recovery gear and me -working hard on seeing the underside of 200 lbs (no wife jokes please ) for the first time in many years.

It's running a D44 in the front, an Atlas 4sp T/C with about 750 miles on it and the 5.13's have about 250 mi on them. Almost its entire life has been spent at 6,000 feet or better.

I reset the gear ratio and tire size (measured at 32" BFG KM2's siped and running at about 32 PSI on stock Moab {Rubi} wheels) with my new AEV pro whatever just yesterday. If you're regearing, buy one of these now! 'Nough said .

Here's the numbers taken from the flatest part of the highway. By the way Red, I sure am glad that Statie had somethin' else to do as I was so busy lookin' down at the gauges and not the speed limit signs.
45 mph 1500 rpm
50 1800
55 a hair under the 2000 mark
60 2100
65 2300
That was as fast as I dare go. Oh yeah the MPG thing never dropped below 18.7 for whatever that's worth.
Now for the best part, I PASSED TWO TRUCKS GOING UPHILL! It's been a long time since I've been able to do that.
It's also the first time in who knows when that I didn't have to turn the overdrive off on that road. I would do this again in a heartbeat.
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