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34's on 3.21 gears

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Old Nov 19, 2012 | 04:52 PM
  #1  
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Default 34's on 3.21 gears

Ok, I have been on this forum for a few months trying to figure out which mods I want. There is a ton of info. on here and I learned alot, but I still have questions. I have a 2012 jku with 3.21 gears, 255/70/18 tires and automatic. For now it is my dd and will not be doing any major off roading (until I regear). I plan on doing a AEV 2.5 lift. I originally wanted 35" tires but realized that with the 3.21 gears, that might not be a good idea. I found Nitto 295/70/18 Terra Grapplers. I checked out the gear chart and it looks like I'm losing about 120 rpms. My question is, will this be noticeable? I only drive about 5 miles a day, but I do take the occasional 300 mile trip to the shore.
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Old Nov 19, 2012 | 05:06 PM
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I have run 7 sets of tires on my 12 auto with 3.21 and never lacked for power here is my gas mileage info all adjusted for tire size
255 stock Sahara 17-20
255 rubi tires moab rims 16-19
33x12.50r20 federal mt on srt8 rims 14-17
285-75r17 on moabs duratrac's 16-19
325-60r18 nitto terrain on Sahara rims 15-17
315-75r17 kumho Ventura mt kmc rims 15-19
35x12.50r18 bfg km2 stock Sahara rims 15-19

Last edited by swaite3; Nov 20, 2012 at 05:59 AM.
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Old Nov 19, 2012 | 05:11 PM
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well, my bud has a 2012 auto with 3.21, on 315/75R17 (approx. 35") MTZ. He drove his jk for about 30 000km with this setup before getting a AEV procal module. And then he corrected his speedo and shift points with the procal, and he saw a good difference on acceleration and he finally was able to run the overdrive on the highway, which he can't before the reprograming.

to answer your question, no it won't be noticeable imo, if it was 500 yes it would, but not for 120. 34" tires and a procal and you'll be good for light offroading.
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Old Nov 21, 2012 | 05:44 PM
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Originally Posted by swaite3
I have run 7 sets of tires on my 12 auto with 3.21 and never lacked for power here is my gas mileage info all adjusted for tire size
255 stock Sahara 17-20
255 rubi tires moab rims 16-19
33x12.50r20 federal mt on srt8 rims 14-17
285-75r17 on moabs duratrac's 16-19
325-60r18 nitto terrain on Sahara rims 15-17
315-75r17 kumho Ventura mt kmc rims 15-19
35x12.50r18 bfg km2 stock Sahara rims 15-19
Which set do you like best?
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Old Nov 21, 2012 | 05:55 PM
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[QUOTE="Dingosirok"]

Which set do you like best?

Well for all around I would say the bfg km2's, the nitto's are the nicest on the road but the sizing I have is a little wide for me. I think I'm going to sell these and get a set of 275-70r18 33.25x11 bfg at's for the street ( I have them on my f150 in this size and they are a great tire )
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Old Nov 22, 2012 | 05:05 AM
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Youll be good with that setup and 35's... thats what I have.... I would only change my gearing if I went OVER 37's
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Old Nov 23, 2012 | 03:17 PM
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Thanks for the feed back. I just ordered the lift kit, tires, procal, and the geometry collection brackets. Now I have to wait till December for the install....any suggestions on a spare tire relocation? I was planning on doing an Aev rear bumper with the tire carrier or the Teraflex tire carrier in the future, but I need a short term solution until the funds build back up!
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Old Nov 23, 2012 | 05:50 PM
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Originally Posted by Dingosirok
Thanks for the feed back. I just ordered the lift kit, tires, procal, and the geometry collection brackets. Now I have to wait till December for the install....any suggestions on a spare tire relocation? I was planning on doing an Aev rear bumper with the tire carrier or the Teraflex tire carrier in the future, but I need a short term solution until the funds build back up!
A34will fit on the stock carrier, what tire did you order?
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Old Nov 24, 2012 | 11:53 AM
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Originally Posted by swaite3

A34will fit on the stock carrier, what tire did you order?
Nitto terra grapplers 295/70/18 they are about 34.5".
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Old Nov 24, 2012 | 04:25 PM
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Originally Posted by Dingosirok

Nitto terra grapplers 295/70/18 they are about 34.5".
You will need to get some wheel spacers but your spare should fit on the carrier without any issues with a 11.5 tire
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