dave7200

I’ve mentioned this before and I wish someone could help me with it. That chart that gets posted once in a while is not right. It says at 70 with 35’s my rpm should be 2081 with 3.73’s. My jeep, at 70 reads 2400 rpm. That’s 70 being cross checked with a GPS. Even saying they are not 35 inches tall but 34 on that chart it says an rpm of 2142. I’ve measured the height of them and they are 34.75 inches tall. According to that chart I have 4.10’s but they are not. I’ve done the driveshaft count. When I ordered the Pro Rock for the front I had them put in 3.73’s as that’s what I thought was in the rear. Then that chart showed up again and had me so worried my jeep did come with 4.10’s that I jacked it up and put it on four jack stands. I locked the front and rear differentials and put a piece of tape on the top of the front and back tire. Started it up and put it in gear. Sure enough both pieces of tape went around in perfect unison. So I was satisfied that it does indeed have 3.73’s and that chart can’t possibly be right. Sorry I'm off topic!!

Dave

MTG

Have a '12 auto with 315/70/17 and honestly can't tell the difference. Climbs up to 10K feet without problem, accelerates fine, etc. Regearing never even crossed my mind.

Moving to 37s soon. Not even sure I'll do it then.

eumel789

Makes sense what you are saying!
BTW: Congrats on the 12 :-)

mattgt5

Thanks man. Hit 16k on the odo this weekend. Stock tires for the first k, 35s fir the next 14k and now 37s for the last k. I really think that 37s will become the new tire of choice with the 3.6 and the new auto. Its just too easy to run them and you dont have all of the performance problems of the 3.8. We will see because it will definately be easier to break "shit" on the trails with the 37.

Black_JKU

Finally!!!! Someone else that feels the way I do!!!!
I've got the same tire/gear combo and I honestly have ZERO need for a re-gear!!!!
Maybe with 37's...... Maybe....

JKbender

I also have 3.21's... Do either of you know what kind of mpg you are getting with these gears and 35's? A lot of people with the 3.8L say that they need the regear to get the mpg back, but you are the first guys with this setup on a '12 that I have run across.

To those who slam, no I did not buy my JK for it's awsome mpg but I drive 110 miles a day min, so I do keep an eye on it.

scemracing

I get 20-21 on the highway but I drive like a grandma. I found with the auto, 3:21's, and 35's I get better mileage by putting into 4th on the highway.

JKbender

Thanks for the info. I am getting 22-24 with the stock pizza cutters, so it does not sound like too much of a change. I keep between 55-65 most of the time as well.

Fir-na-tine

I have a 2012 JaKe with 3.73 gear sets running 35" Toyo's and driving on the highway keeping my rig rpms at 2000 /68 mph i have ranged from 18.2-18.8 MPG.......Off the line speed is still impressive given the extra weight over a bone stock JK........I paid $50 extra for the optional 3.73's over the stock 3.21's.......making that change at purchase saved me $$$ doing a gear change later.......I'm happy with the 3.73's and feel no need whatsoever to change them......even if i go with a taller tire for DD use it's only going to lower my RPMs at that speed anyway.......my thoughts

Cheers

eumel789

I don't know if they beefed up the axles for 2012 for 37s. We will see what breaks, if anything. It was, however, the same with 07-11 models. It was feared that the 35s will break everything. Well, that did not happened, except for some real hardcore wheeling. The jury is even still out on gussets and sleeves for the front axle.