After looking around I have some thoughts about regearing for 33s and 35s.

This is the formula I was using for figuring tire size and axle ratio compared the to stock config:

29"x4.88s/33"=4.29 So if I ran 33s on 4.88 gears it would be essentially like I was running 4.29 gears on the stock 29" tires.

29"x4.88s/35"=4.04 So if I ran 35s on 4.88 gears it would be essentially like I was running 4.04 gears on 29" tires.


I used this formula to figure what gear and tire size I should be running with 33s or 35s:

33"x3.73s/29"=4.24 So if I want to run 33s I should run as close to 4.24 gears as possible. Go numerically higher for better off road or around town, or go lower for better highway. 4.56 for around town and off road, or 4.10 for highway.

35"x3.73s/29"=4.50 So if I want to run 35s I should run as close to 4.50 gears as possible to bring as close to stock configuration. Which would be 4.56.


So from what I can tell, running 4.88s is going to kill my highway driving but might improve my mpgs around town and I'll have better crawl ratio off road. Which could prevent me from springing for a new low crawl 4:1 t-case or bolt on low gear kit. Problem is, if I want to drive to Moab, the jeep won't like being pushed to 75 mph on the highway.



Thoughts?

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My Jeep Build ----> Big Black

having the 4:10's w/ 35's it worked but i didn't have the power when i went past 70mph it wouldn't hold the speed...the jeep liked 65-70 range...i haven't been on the highway w/ the 4:56 yet but will let you know...

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02 Jeep TJ Sahara, 33's locked up front
03 SAS KJ 0n 35ish boggers(Sold )
Petersens 4wheel: http://www.4wheeloffroad.com/featuredve ... index.html

You also got to figure in engine torque in your quest for gears.If you have a TJ with the 4.0 I6 then you stay on the higher side of the gears but the 3.7 needs the lower side of the gears.Plus the added weight of the tires and the KJ being heavier you will need lower gears then what that math equation is telling you.

Just remember I'm running 4.10's with 32" tires and have no power(nowhere near OEM).

So far I am pretty happy w/ the 4.56's w/ the 33's. It accelerates fine and holds 75mph no problem on the flats. Uphill the trans gets a little funny but not as bad as when stock and just clicking off the OD it pulls grades OK until it gets steep enough to require 2nd gear.

I do not think that I would be happy w/ 35's on the 4.56's on or off road.

When/If I move to 35's, I will definately be going to 4.88's or 5.13's.

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99 TJ
71 C101
04 KJ
03 SFA KJ Sport
LOST JEEPS So-Cal

Good info guys, thanks. I am going with the 4.88s for sure just to save the chunk of change of regearing front and rear. This way the front axle is done already.

Troy, I thought about what you were saying and that makes sense. The KJ seems to have less get up and go than my old TJs did even with more torque and power with the 3.7 vs 4.0. I would have to assume that is the weight of the KJ and going to deeper gears would help that I would hope. I wish I could drive someone's around to see. One with 4.56 vs one with 4.88. I think the 4.88s will be fine either way and better suite me for when I eventually go with 35s which I know I'll be too tempted to avoid forever.

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My Jeep Build ----> Big Black

Found this chart too, the yellow is for MPGs, black is middle ground, and blue is performance.

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My Jeep Build ----> Big Black

i don't need a speed demon of a jeep i rather get the gas milage...drove 180miles today on a full tank w/ 25% town driving...

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02 Jeep TJ Sahara, 33's locked up front
03 SAS KJ 0n 35ish boggers(Sold )
Petersens 4wheel: http://www.4wheeloffroad.com/featuredve ... index.html

So how was it driving at highway speeds? 180 miles for a whole tank? I am getting like 265 miles on 18 gallons right now, city driving.

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My Jeep Build ----> Big Black

What height tire is that 265 miles on? It seems low. I got about 330 miles stock, and about 320 with the 245 MT/R's, and I am not easy on the go pedal. The figures where higher on summer formula gas.

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LOST # 633
'05 KJ 3.7L/6spd/241 245/75/16 MT's
'88 MJ 4.0L/AW4/231 SWB HPD30 & trac-loc D44 w/3.73's
A dirty Jeep is a happy Jeep

31x10.5x15 with 15x8 steel wheels

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My Jeep Build ----> Big Black

I guess I won't complain about my mileage then.....

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LOST # 633
'05 KJ 3.7L/6spd/241 245/75/16 MT's
'88 MJ 4.0L/AW4/231 SWB HPD30 & trac-loc D44 w/3.73's
A dirty Jeep is a happy Jeep

If you gear correctly,going to 4.88's at least for those 35" tires,you will get better mpg's then what you are getting now.You are over working your engine and that is why you are only getting 10mpg's even on the highway.

i know that that's why i am regearing...it's hard to stay at 70mph...look on the bright side...the jeep drove straight and true and i can officially say that the jeep is tuned and riding great...tomorrow i will have a secret to reveal to you all that i think the east coast ppl might like...

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02 Jeep TJ Sahara, 33's locked up front
03 SAS KJ 0n 35ish boggers(Sold )
Petersens 4wheel: http://www.4wheeloffroad.com/featuredve ... index.html

Man now I wish that I was East Coast ....maybe

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MUDD'S MOTORSPORT'S We do IFS lift installs ,
03 OVERLAND EDITION /Kilby-Skidrow-Mopar-4XGuard skids/ 2.5 inch TOTAL CONTROL JBA coilovers -JBA Arms/MOABS-31 FALKEN WILDPEAK AT3W / 4.10's etc, 04 Kilimanjaro Edition loaded, plus 05 KJ limited

MOTHER EFFER! you can't be serious

That's bloody good gas mileage

that's w/ the 35's and 4:10...oh don't forget to factor in the extra weight of the jeep, roof rack, it also being muddy doesn't help millage...I'm happy w/ that...

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02 Jeep TJ Sahara, 33's locked up front
03 SAS KJ 0n 35ish boggers(Sold )
Petersens 4wheel: http://www.4wheeloffroad.com/featuredve ... index.html