I’ve done a pretty good bit of research on this and other forums regarding gearing as it pertains to bigger tires, gas mileage, powerband, etc. However, most of the info I've found for the 2012, specifically, has been kinda sporadic.

Given its flatter power curve and added hp, the 3.6 Pentastar engine would seem to alter a lot of what I’ve read about gearing in the earlier model years. Maybe a little, maybe a lot. I don’t really know.

I’ve looked at the power curve charts, although they seem to me to be a fairly broad generalization, considering all the variables that make one Jeep so different from the next. I’m going to be running 35’s on a 2012 MANUAL JKU.

I won’t be rock climbing, or trying to summit the north face of Eiger. I will not be towing anything.

I will do some recreational off-roading…probably on woods trails. I will get into some mud and snow. Nothing too hardcore.
I’ll also do a good bit of long-distance freeway/turnpike driving, so keeping mpg loss to a minimum is desireable.

Taking all of this into consideration, I’m looking at upgrading my gearing to 4.88. Again, that comes from looking at posts that deal mostly with other year models, and mostly with automatic transmissions. I skipped the 4.56 because I’ve read that they are less available and more expensive. Correct me if I'm wrong.

Nevertheless, I'm not certain that I'd really NEED to go to 4.88's. Would 4.10's be enough?

I understand that I’ll be running at higher rpm’s at freeway speeds than with my current 3.73's, either way. As long as it’s not gonna overly abuse the engine, trans, etc I’m okay with that.

My plan is to find a mechanic/shop that I can trust to do the job right, then order the parts through them.
I also intend to buy everything new. Front/rear gears, bearings, pinion nuts, shims, etc. Not sure exactly what I’ll need…that’s one of my questions to you, the knowledgeable. Is it called a master kit?

Not sure where I got that from…

I do remember reading a post somewhere that the rear pinion bearing and some other parts would probably be trashed during the gear change, and that it would be better to spend a little extra $$ and get the job done right, as opposed to skimping and having something fail post installation.

My philosophy as well.

To boil it all down, let me ask this:
What gearing would best optimize highway driveability, while still giving me decent gas mileage, based on my having the 3.6 with a MANUAL transmission?

Like doing a handstand on a tightrope, I know.

Any and all advice would be greatly appreciated.

 

2012's too new at this point?

 

I have a '12 w/ 6 speed manual w/ 3.73's.....I drove a 2 dr. w/ the 3.21's and it felt like it did not have enough a$$ to it....the gears were longer....but would not work well w/ a bigger wheel & tire set!

 

Kwolf, you got it figured out!
Yes you want 4.88's they will make you and your Jeep happy with a 6 speed...2012
A good installer wont need complete install kits but it wont hurt, just a little more money..
4.10's and your gonna be lugging it a bit, 513's and you'll be spinning a bit more than needed.
I have a 2012 with an automatic and 35's I'll be installing 4.56's in mine soon.
You could run 5.13's or 4.10's 4.88 should give you the sweet spot
I set gears here at my home shop, been doin it for years..but my time is tight plus I'm an hour south of Chicago.
Good luck finding a installer you can trust!
$500 to do the job is fair if done right!
Gene

 

thanks guys. Not a lot of info out there yet about the 2012's...manual trans, even less so.

'Preciate the help.

 

I thought that the '12 rigs are on hold for gear swaps until the ecm/pcm software can be figured out? Last I knew swaps are a no-go because of when he Jeep comes off the lift and is driven for the first time the software puts the Jeep in "Limp" mode as the new ratio cannot be flashed into the ecm? Has it been figured out yet?

 

This was only a problem on the auto trans - and it has already been fixed in the latest version of AEV's procal.

 

AHA! Why Roger that then