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Old 07-11-2012, 08:10 PM   #1
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2012 w/3.21s and Lift/Tires-Results!

I bought my 2012 JK (2 door, soft top, auto) with 3.21 gearing. Ah, the horror.
Kidding: with no mods. 3.21 gearing is just fine and I was perfectly happy. It wasn't until AFTER I'd ordered my 35" tires and lift that I stumbled onto the gear chart on this forum. I realized then that I might have just built a 2012 Turtle Edition JK. Did I mention I am a lead foot?
I am not posting this to debate tire weight vs. rotation vs. tread vs. gear ratio vs. 15 wheels vs 17 wheels vs. 3.6 or 3.8-just my results with 3.21 gearing and tire change for other people with 3.21s on a 2012.
I originally bought 35" Open Country Toyo MTs with MKW M80 wheels. (I don't recommend the wheels- and they are heavy.) I returned the Toyos pre-lift install. I went for 305/70/17" KM2s- much lighter and with a narrower tread. The new 3" Mopar lift is installed and the KM2s are on- along with a Procal tire size programming change.(It makes a difference).
Do I need a gear change? No! Mostly. The difference is very minimal- and believe me I was looking. We made note of what gear we were in (stock) on certain roads and after the Procal/34" install it was very, very close. The crappy 40 MPH low torque problem is still there. I was happy as a fiddle until I turned on the AC. Its not crazy slow- but I noticed a change primarily on the freeway. This is the ONLY time I find myself mashing the pedal more than normal. Or downshifting. Or moving into the slow-er lane.
I won't be re-gearing- I can still pass easily (with mashing) and I have no problems city, uphill or on trails. Plus who needs AC? There are too many other mods I want for the $1500 4.10s would cost me- and frankly I'd be forking over that cash in anger- at myself for not getting 3.73s. (No need to rub that one in by the way- and no offense to my fellow 3.21'ers).
Don't ask me about gas mileage. It sucks. See "lead foot" above. MPG went down.
I still covet the Toyos- but I'd only switch to a (heavy/wide) 35" MT in concert with a gear change. Pretty certain I'd need it. Donations accepted!
Thanks to everyone who helped me with all my questions prior to install!
If you have 3.21 gearing on a 2012 & a similiar set-up please post your results so we can keep the thread going/help those looking to do the same.

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Old 07-11-2012, 08:19 PM   #2
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Looks good and it's good to have someone take the time to post their findings like this. Always appreciated. x2 on getting the 33s instead with your gears/set up. I've got the same set up but with a 2.5 lift 33x12.5R15 Mickey Thompson MTZ and 3.21 gears on a manual.

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Old 07-11-2012, 08:29 PM   #3
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Speaking of helpful posters...thanks!
Do you have two Jeeps? I thought you put on KM2s after your Duratracks? Or have I lost track?
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Old 07-11-2012, 08:31 PM   #4
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Originally Posted by JeepHerz
Speaking of helpful posters...thanks!
Do you have two Jeeps? I thought you put on KM2s after your Duratracks? Or have I lost track?
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Old 07-11-2012, 08:36 PM   #5
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Old 07-11-2012, 08:40 PM   #6
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Old 07-11-2012, 08:44 PM   #7
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x2 :d
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Old 07-11-2012, 08:47 PM   #8
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I have a 2012 jk unlimited with 3.21 gears and I'm running nitto terra grapplers that are ~33s as well. I just don't get to use 6th gear
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Old 07-11-2012, 08:53 PM   #9
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I have a 2012 jk unlimited with 3.21 gears and I'm running nitto terra grapplers that are ~33s as well. I just don't get to use 6th gear
That's because they're nittos.
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Old 07-11-2012, 09:05 PM   #10
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That's because they're nittos.
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Old 07-11-2012, 09:09 PM   #11
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Its ok young padawan, he's talking about 33s not 35s. Your safe.
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Old 07-11-2012, 09:14 PM   #12
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Looks good and it's good to have someone take the time to post their findings like this. Always appreciated. x2 on getting the 33s instead with your gears/set up. I've got the same set up but with a 2.5 lift 33x12.5R15 Mickey Thompson MTZ and 3.21 gears on a manual.
This will be my exact setup as well. 2.5'' lift and 33x12.5R15 but I'll probably go Goodyear Duratrac's. I figure with the manual and 3.21's it will be the best I can do without regearing and should be plenty for the wheeling I enjoy doing with my DD.
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Old 07-11-2012, 09:22 PM   #13
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This will be my exact setup as well. 2.5'' lift and 33x12.5R15 but I'll probably go Goodyear Duratrac's. I figure with the manual and 3.21's it will be the best I can do without regearing and should be plenty for the wheeling I enjoy doing with my DD.
Perhaps you've not seen my "other" thread. BEHOLD!!

http://www.wranglerforum.com/f33/33x...deo-96568.html
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Old 07-11-2012, 11:28 PM   #14
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Oh believe me I have and that's a lot of my reasoning behind the setup. I haven't checked it in a while but if I remember you were having some balancing issues. I'll need to check the latest on that one.
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Old 07-11-2012, 11:43 PM   #15
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Good Read - I am glad I have max towing with 373 though.
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Old 07-11-2012, 11:44 PM   #16
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Good thread. 2012 Jkur here with 410s automatic and 37s no loss of power. Will regear to 538s when we buy 40s
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Old 07-11-2012, 11:53 PM   #17
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Great thread.
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Old 07-12-2012, 04:10 AM   #18
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Good thread. Makes me feel okay about having 3.73's and going with 315/70/17's!
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Old 07-12-2012, 04:19 AM   #19
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do they even have 4.10's for the jk dana 30? I haven't seen them. I take that back...I think mopar sells a set but I haven't seen any others. just 4.56 and up
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Old 07-12-2012, 06:04 AM   #20
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Looks good, what size did you use on the Procal? From what I have read and used on my JK the actual tire size is often smaller than what is listed.
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Old 07-12-2012, 06:11 AM   #21
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Oh believe me I have and that's a lot of my reasoning behind the setup. I haven't checked it in a while but if I remember you were having some balancing issues. I'll need to check the latest on that one.
Yes I did and I don't run the duratracs anymore. I have mickey thompson MTZ currently and they balanced fine.
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Old 07-12-2012, 06:12 AM   #22
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I installed my 3" lift last week and yesterday put on my 15x8 wheels and 33x12.50 Duratrac's. Waiting for my Procal to make the tire change and tpms. Drove it around town and not bad, but sure it'll be a little better with the Procal.



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Old 07-12-2012, 06:20 AM   #23
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I installed my 3" lift last week and yesterday put on my 15x8 wheels and 33x12.50 Duratrac's. Waiting for my Procal to make the tire change and tpms. Drove it around town and not bad, but sure it'll be a little better with the Procal.
Looks good.
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Old 07-12-2012, 12:31 PM   #24
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Looks good, what size did you use on the Procal? From what I have read and used on my JK the actual tire size is often smaller than what is listed.
Good point. KM2s run smaller than "standard." Ie: a 34" KM2 is not 34". I bought PMetric so they're an odd size anyway. Mine are 33.9" tall- I used 34". I know that makes it a little off but I am not too worried.
I plan to try changing it to 35"s and see if I can trick it into better gear shifts. I wanted to get a full tank or two in first. I doubt it'll work but I'll give it a try. I love that gadget.
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Old 07-12-2012, 12:35 PM   #25
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I installed my 3" lift last week and yesterday put on my 15x8 wheels and 33x12.50 Duratrac's. Waiting for my Procal to make the tire change and tpms. Drove it around town and not bad, but sure it'll be a little better with the Procal.
Do you have any drive shaft concerns? My understanding is over 2.5'' you run a risk of drive shaft damage.

Looks good btw
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Old 07-12-2012, 12:43 PM   #26
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Good point. KM2s run smaller than "standard." Ie: a 34" KM2 is not 34". I bought PMetric so they're an odd size anyway. Mine are 33.9" tall- I used 34". I know that makes it a little off but I am not too worried.
I plan to try changing it to 35"s and see if I can trick it into better gear shifts. I wanted to get a full tank or two in first. I doubt it'll work but I'll give it a try. I love that gadget.
Most tires are smaller than advertised. Even the stock KM's.
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Old 07-12-2012, 12:56 PM   #27
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Do you have any drive shaft concerns? My understanding is over 2.5'' you run a risk of drive shaft damage.

Looks good btw
Concerns, yes. I've been reading up on the thread about the 3" lift and up.
Since the lift is a week old and wheels/tires put on yesterday no problems yet of course, but I want to remedy the situation before it becomes a problem. it'll be a bit before it goes off road, but want to get the parts I need to fix now so its over with. Adams drive shafts seem nice, but not sure if I need lca's or what not as well....
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Old 07-12-2012, 03:01 PM   #28
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Concerns, yes. I've been reading up on the thread about the 3" lift and up.
Since the lift is a week old and wheels/tires put on yesterday no problems yet of course, but I want to remedy the situation before it becomes a problem. it'll be a bit before it goes off road, but want to get the parts I need to fix now so its over with. Adams drive shafts seem nice, but not sure if I need lca's or what not as well....
if you install a new front drive shaft and your jk is at 3" or above it means that your caster with stock control arms is less than stock 4*, meaning you will not need to install new front lower control arms unless it's flighty on the freeway. but having a new front drive shaft will not make it any more flighty than it is now without one.
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Old 07-12-2012, 04:18 PM   #29
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if you install a new front drive shaft and your jk is at 3" or above it means that your caster with stock control arms is less than stock 4*, meaning you will not need to install new front lower control arms unless it's flighty on the freeway. but having a new front drive shaft will not make it any more flighty than it is now without one.
Thanks for the reply. So say I get the Adam's drive shaft, I should be good? I just don't want any problems in the future.
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Old 07-12-2012, 05:44 PM   #30
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great thread. Sub'd

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