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Future lift, but worried about gears

2K views 21 replies 14 participants last post by  Shuffler 
#1 ·
I have a 15' JKU Rubicon, i have my bud sheet and i confirmed i have 3.73 gear ratio. I did some research (google/youtube) will a 3" lift, and 35" tires affect my daily driver? If thats the case, should i consider going for a project in changing to 4.10/
 
#3 ·
In my opinion, if you have not done the lift yet, a 3" lift is excessive for 35" tires. And yes, a change to the suspension and steering geometry will change the driveability of your Jeep. It can change it for the better if you spend the money to do it properly. If you throw crap at your Jeep, it will drastically decrease the performance and make you very unhappy.
 
#5 ·
My brother ordered 4.11 gears on his Rubi when he bought it. He runs 37.5" tires and it runs fine. At 75 mph on the highway the eco light is on.

For 35" tires you should be fine with 3.73 gears. By chart it calls for 4.11 but it depends a lot on where and how you drive.
 
#7 ·
And as I've said before my 3.73 with stock 32s here at sea level is not only fine, I feel like I have room to go up in the size from a gearing perspective.

For instance shooting a gap today I managed to slide it sideways in light rain breaking the rear loose.

Also I have enough torque to run it in any gear from 3rd to 6th from 40 mph on up, and 1st seems particularly short < 15 mph.
 
#8 ·
3.73's is not BAD on a JK with 35's for most people. It is not like it is stock though but most people it is livable. It also has a lot to do with where you live and how you drive.

For a lift, I would do a 2.5" for the 35's. And yes, it will effect your ride and handling but if done right, it will make it a lot better! Here is two great lifts we sell that make the on road ride and handling much better and will work just fine for 35's:
http://www.krawloff-road.com/product_p/kjeeper10.htm

http://www.krawloff-road.com/product_p/kor-rkjk25fs-kit.htm

If you have any other questions, please let us know!

-Jason
 
#10 ·
2013gecko said:
I routinely drive I70 through the mountains of Colorado on 35s with 3:73 gears automatic 3.6L. I have 0 issues both on the inclines and declines
Key point being the OP is talking about a first generation JK which is completely different than the 2012+

Gearing is more critical on the first generation especially because of the transmission that was used during those years and partly because of the 3.8L power band being what it is.

I have owned both a 2007 JKU and now a 2014 JKU

I ran 5.13 gears in my 2007 and 4.88 in my 14. I could have went with 4.56 in my 14 but wanted a little extra.
 
#11 ·
Prot said:
Key point being the OP is talking about a first generation JK which is completely different than the 2012+ Gearing is more critical on the first generation especially because of the transmission that was used during those years and partly because of the 3.8L power band being what it is. I have owned both a 2007 JKU and now a 2014 JKU I ran 5.13 gears in my 2007 and 4.88 in my 14. I could have went with 4.56 in my 14 but wanted a little extra.
In the first post it states the OP's Jeep is 2015.
 
#17 ·
I have 35s on our 2014 4dr auto and 3.73 gears (4.56s are in the garage waiting for install).

While it gets around "ok", it is far from properly geared. It shifts and searches more than it should, runs higher RPMs than it should, is not as responsive as it should be, and I wouldn't tow anything with it.

4.56 gears will pay for them selves in fuel economy, making the Jeep more capable and enjoyable to drive.


You gotta know what your missing before you can complain about it.
 
#20 ·
My brother just returned from a 2 week trip around the gulf coast to Florida's Atlantic coast and back. He averaged just over 18 mpg. That is with 37.5s and 411 gears. There are charts available to help you choose. If you live in the mountains and had this JK you would want 4.56 minimal. In the mostly flatlands 4.11 is acceptable.



Interestingly enough the 3.8 chart is the same.
 
#21 ·
Those charts are nice to look at and useful if you want a general idea/starting point, but they leave too many factors out to be considered a go to guide.

There are more factors to consider than just RPMs at a certain speed in final drive gear.
 
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