If you have a 2007-2011 JK, especially with an AUTO trans, regearing will be very crucial to drive-ability and off-road performance with larger tires.

If you have a 2012, it MIGHT be, but make sure when you are researching on this forum you pay close attention. Most posts on the forum, including several in this thread, are concerning JKs with the 3.8 engine/tranny combo. With the 2012 models, traditional JK wisdom will not always apply. I posted the gear/tire size charts a few posts back, and they are also available in the FAQ and a thread by Jpop. Some members have already over-geared with 4.88 or 5.13 gears for 35" tires and posted warnings about it. Many are hoping for a 4.30 gear set for the Dana axles to start being produced, which would be a really good gear set for 35's. 4.30's have been a popular gear set for non-jeep vehicles in the past.

 

My from my personal experience, I am no expert on gearing by any means:

I have an '09 4dr w/ 3.73's and auto trans, within the first month I lifted with 2.5" coil spacer and put 33's on it (285/75R16) on 16x8 steel wheel; then proceeded to take a 1300 mile road trip. The Jeep did pretty well but had a little trouble passing with a head wind at 75+ mph, I was expecting this so not a huge issue for me personally (shoot it's a Jeep, not meant to go fast, meant to perform off-road). I then added a CAI, TBS, and cat back exhaust, which for the "butt in seat" feel it seemed to help, but wanted a little more pep and new I would soon go to 35's, so I now have a SC Flashpaq, which did help for again that "butt in seat" feel (I also like the added options that come with a tuner for correcting speedo, TPMS, etc...). Since then I have upgraded to 35's on alum wheels (which was nice because the actual change in weight from previous setup to new was almost negligible) and with my current setup I have no issues and I am happy so far with performance on road. I will say this though, I do plan to regear in the future to probably 4.88's to alleviate some of the strain on the drive train.

Since you're running 3.21's and new 3.6 Pentistar (although I wasn't completely impressed with the new engine when I test drove one; can see my review here: https://www.jk-forum.com/forums/show...MW3-Pics-here!) I do not have a great answer for you and my story above is simply for comparison only. My friendly advice, if you don't plan to go larger than 33's on a dual purpose rig and do minor wheelin' I would say for financial purposes go with a tuner. If money is no object, I would probably look to regear first, then maybe look into a tuner after that; but then again what do I know.

 

You might want to specify whether you drove an auto or a manual. From what you say, I'm guessing you had a manual, with the OD being better for oversized tires.

 

I have never said 35's and 3.21 gears would be a good combination, because it wouldn't. I have simply been making comparisons to show how gearing helps with load on the engine. Your twisting things around yet again. I realize the differences between the 3.6 and 3.8 motor and transmissions and have drove both. As far as the OP, and not going over 33's, although not ideal in my opinion, it will be liveable only because of the improved engine and transmission, and if and when a tuner becomes available for them, it would help even more, especially with advanced transmission tuning

 

Shoot my bad, will update my original post... But to answer I have an auto

 

Please explain how I "twisted things around." If you're talking about the 35's and 3.21's, I was "twisting," I think we were just on different trains of thought. I'll lay out the conversation for you, so you realize I had no bad intentions.


At this point, as with all my posts, I am STILL referring to the original thread, which addresses a 2012 Auto with 3.21 gears.

<--I'm guessing this is where we got mixed up, because it seems like you thought I was talking about 4.10's.

<--And here is my first attempt at squashing the whole overdrive debate, which we both seemed to agree on.

<--And here's you accusing me of "twisting" things around.

I have done nothing but answer the OP's question, which was originally about strain on the engine, and he also mentioned cost. I think I've been pretty straightforward with YOU and the OP in all my posts, and I have backed them with actual facts that support what I have said.

 

To the OP, with 3.21's and a 2012 Auto: with 33's, you will have more power than Wads's JK had on 3.73's and 33's.

Of course, 3.21's is not the gear set any of us would pick to go with 33" tires, but after you buy wheels, tires, get them mounted, guy new gears, and have them installed, you probably could've upgraded to a RUBI.

 

Not looking for an argument, I feel this statement is more a matter of opinion than fact, depends on what you go with, how you handle the mod'ing, etc... And depending on the mod'ing that you do, why pay a premium for the Rubi stuff when you're just going to mod that stuff as well.

 

Well you're right. Guess it would all depend on all the costs.

 

Load on an engine is load... Gearing will not change the load seen at the flywheel. 'That' is all in your right foot.

How that engine torque gets transferred to the tires is where the transmission and gears come into play. Deep gears transfer a lot of torque to the axles. Taller gears, not as much.

Shorter gearing (4.10's on 32's) will not necessarily mean bad mileage or a winded engine. I ran that combo for almost 100k miles. I am a fuel miser, and found my best mileage maintaining 2400rpm in the 3.8L. Lower, and I needed slightly more pedal to make simple grades on the highway.

My opinion - run the deepest gears you can tolerate.

And of course, a tuner will not substitute proper gearing