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Old 08-04-2012, 05:21 AM   #1
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Gear ratio 3.21, what to do

I recently bought a 2012, wrangler, unlimited, altitude, automatic, with a 3.21 gear ratio, didn't do my homework. I plan on putting a 4" lift with wheels and 35" tires. Can I live with the 3.21 a while with the 35's or will it be unbearable, undrivable? Can I pull my boat with 3.21 gears and 35's? Should I re gear to 4.10 or 4.56 for mainly on-road use, boat pulling, light off-road, no rock crawling? What all will I have to change to go from a 3.21 to a 4.10 or 4.56? Just registered with wrangler forum today. Look forward to it

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Old 08-04-2012, 05:27 AM   #2
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35's I would re-gear to 4:56 or 4:88

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[B]2006 Jeep Unlimited RE Express 4 1/2" Lift, JKS 1.25" BL, 37x14.50R15, Toyo Open Country Tires, Tom Woods Drive Shafts, SYE Kit, D30/D44 4.88 Gears, Warn 8000 lb Winch, Cobra CB, Viair On-Board Air, Bushwacker Flat Fenders, and Lots of light
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Old 09-06-2012, 12:37 AM   #3
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have 2012 wrangler unlimited automatic..have 35's on it........didnt shift at right time......so just put 4.88 gears.....got it out of shop today.......wont shift out of 2nd gear....guess the computer chip has to be reprogrammed...4wd shop couldnt do it so took it to dealer and they had no idea how to reprogram it for the 4.88 gears....so tomorrow i will b looking for someone that can.......fyi...a little headsup for you for when you have it done.
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Old 09-06-2012, 12:41 AM   #4
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Originally Posted by 2012 Red View Post
have 2012 wrangler unlimited automatic..have 35's on it........didnt shift at right time......so just put 4.88 gears.....got it out of shop today.......wont shift out of 2nd gear....guess the computer chip has to be reprogrammed...4wd shop couldnt do it so took it to dealer and they had no idea how to reprogram it for the 4.88 gears....so tomorrow i will b looking for someone that can.......fyi...a little headsup for you for when you have it done.
The Hypertech programmer should be able to correct that shouldn't it?
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Old 09-06-2012, 12:50 AM   #5
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Throw em in the trash & install either 4.88's or better yet 5.13's like I did. Love it!! It's like adding two more cylinders to that 3.8!
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Old 09-06-2012, 07:20 AM   #6
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Originally Posted by WILLIAMHALE1 View Post
I recently bought a 2012, wrangler, unlimited, altitude, automatic, with a 3.21 gear ratio, didn't do my homework. I plan on putting a 4" lift with wheels and 35" tires. Can I live with the 3.21 a while with the 35's or will it be unbearable, undrivable? Can I pull my boat with 3.21 gears and 35's? Should I re gear to 4.10 or 4.56 for mainly on-road use, boat pulling, light off-road, no rock crawling? What all will I have to change to go from a 3.21 to a 4.10 or 4.56? Just registered with wrangler forum today. Look forward to it
With 3.21 gears on a '12, you're gonna have issues with the 35's alone, much less towing.

On an auto, you'll find it wants to hunt and peck for gears when you go up hills or try to pass on the freeway. It'll kick in and out of OD constantly in those two situations. And that's without towing anything.

I'd recommend going to 4.56 gears. If you live in the mountains or do the majority of your driving in the mountains, I'd go 4.88.

There is a big difference between gearing needs for a 3.8L Jeep and your 3.6L.

Gonna run you ~ $1500 for a regear, depending on where you live. Find a shop that specializes in gearing, and order your gears through them (you want a master kit). That way both the mfr and shop warranties will be good. Yukon, Alloy USA, Superior and USA Standard all make good gears – and most gears are made by CHA Industries, so any of em will do.

There'll be a break-in period for the new gears; make sure you follow it religiously, unless you wanna pay for it all over again sometime down the road.

Here's a good thread on gearing. First page deals with the 3.6L Jeeps; 2nd and beyond deals with the 3.8L engine. If you really want a good understanding of gearing and how it affects your Jeep's power output, mileage, etc in all situations, read the whole thread.

Want 35s dont want to REGEAR ??

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