We just purchased an 08 JK with 6-Speed, 33 inch tires and stock 3.21 gears. The Jeep is used mainly for driving in the Texas Hill Country and some off roading.

I want to replace the stock 3.21 gears with Yukon 4.56 gears, but my wife is bulking at the $1300. She thinks the Jeep runs fine with the stock gear and the Superchips performance mod which is averaging 16MPG

How do I justify spending the $1300 to have the local shop replace the gears?

thanks

Doug

 

get bigger tires, and it will become a NEED haha. Seriously though, I have been running 35's with 3.73 gears now for 2 years and yeah its been driveable but its nothing special. I am finally about to do go to 5.13s, cant wait! also, you live in TX..I think lunatic customs has a gear special for like $1000. check them out. Good luck!

 

If it's the wife your justifying it to that might be tough. I personally am doing the exact same thing as you. 3.21 to 4.56 my justification is that I F'd up and bought a Jeep with 3.21's. I mean they didn't even produce many with that gear set and I think I know why. Look at the awesome gear/tire size chart and you can see that 3.21's just are not suited for any sized tire. I hear tonnes of people asking me why change gear size for only 33's? and I am guessing when they ask me this they don't have 3.21's. I find my Jeep damn near unbareable to me it feels like I am drivng in a head wind with sail up all the time or that I am driving a vehicle twice as heavy as what it actually is. I cannot maintain 100 km/h or 60mph if there is any kinda wind or even the slightest grade and I am switching gears like a semi truck driver if there is hills. If it makes you feel any better I am driving from Northern Canada to Northridge in Washington for my gear change somewhere in the neighbourhood of a 1000 miles one way to get this. But my wife is cool with this so it made it easy...she says it drives fine too but she says its my toy so it's whatever I think. And my thoughts are the Jeep needs a lot less weight, a lot smaller tires, or a lot more motor to be running 3.21's.

 

Maybe undo the Superchips tune without her knowing so your performance drops and then use that as your excuse

If you do a lot of highway driving I would rethink the 5.13's with your 35's. I had 5.13's w/35's and it was terrible on the highway, way too much gear.

I agree completely. My Unlimited has 3.21's with the 16" stock baby tires and the gearing still makes no sense!

For front and back? Not unless you install them yourself.

 

I have to draw the line at house cleaning Oh I did clean the spring clean the entire house while she was pregnant

Maybe I should work the safety angle for my justification

 

I cant use this line as she has had Jeeps in the past.

 

Not sure if everyone gets better gas mileage like I did going from 4.10's to 5.13's. I am getting 2mpg better on average so that translates into gas savings. Let's assume you get the better mpg and drive 10,000 miles a year.

Gas at $3.50 a gallon

10,000 divided by 16mpg = 625 gallons at $3.50 = $2,187.50

IF you get 2mpg better

10,000 divided by 18mpg = roughly 556 gallong at $350 = $1,946.00

So you save about $241 a year assuming you drive that many miles and gas stays at current prices and doesn't hit $5 a gallon like some are predicting. Plug in whatever numbers sound reasonable to you to see how it adds up.

At that savings, you would have to drive the Jeep over 5 years to break even.

Something to think about in addition to the fact that if you do add any mods at a later date, every pound you add to the Jeep really kills performance. That was the reason I re-geared. With all my mods, I felt like I was driving a tank. The added mpg was an unexpected bonus but it made sense that the engine now doesn't have to work as hard to move and maintain speed.

Caveat***** Some people claim worse mpg after re-gearing due to the higher rpm's . So my results may not be what you get. Hopefully someone can chime in on this and maybe expand.

 

I justified it by thinking I would actually enjoy driving it with different gears. What I was having trouble justifying was paying for something that sucked.

 

$1,300 is cheap. I live in MD and I couldn't find gears and carrier installed for under $2,000. I closed my wife who is a jeep driver with the fact that bigger tires will put a lot more stress on the gears and can cause a breakdown. She agreed and also asked what else we should do to protect the jeep. I ordered gussetts and intake. She is happy so far even thou it was a little over 2K. I am having the gears installed right now and cant wait to get it back. I went to 4.88's since I am running 35"s. East coast gear supply is very cheap on the gears if you need somewhere to order good quality stuff.

 

Have her drive it for a while as a daily driver, then she'll get it.