SteelBlueOffroading

I have an 08 2dr 6 speed manual jk with a 3" lift and 315/70/17 Kelly Safari TSR's (basically a 35" tire). I need advice on what gears to run when I decide to regear. I live in NC most rolling hills. The stock 3.73's are just terrible. It will be my daily driver and off-roader but wont be doing much interstate driving. Thanks

TJM12

I have a JKU with the 3.8 motor and I also have a lift, 35's , bumpers, winch, armor, fenders etc. my rig is pretty heavy. I went 4:56 and it made a world of difference but that extra little bit of grunt the 4:88's would have given me would have been perfect. In a lighter 2 door 4:56 might be ideal but personally if I had a do over I would do 4:88's.

Dirty Minded

Is there a reason why you went with the 4:56 instead of the 4:88? Does the 4:88 cost more? Does 4:88 negatively affect gas mileage? Create other problems? Just wondering what factors you weighed when making your decision.

JKRVEE

35" should run a 5.13 if it's the 07-11 jk

TJM12

The guy that did my gears said he personally would never go lower than 4:56 in a Jk, something about the pinion having so few teeth or being very weak, something like that. I figured I wouldn't go against his recommendations especially given that he wouldn't warranty his work if I went lower than 4:56.
Actually 4:56 tends to cost more for some reason?
Gas mileage actually improved because I'm not pushing the tack up in 3000-3500 rpm range just to maintain speed anymore. It feels pretty decent to have use of all six gears again.

TJM12

That's more for the automatics not the 6spd like the op drives.

planman

Actually, if he doesn't travel over 70 mph (interstate driving) very often, 5.13s would be the better choice with 35s and an 07-11 6 speed--if he wants better off road performance.

5.13s result in less than 150 rpm more than 4.88s at 70 mph with 35s and an 07-12 6 speed.


4.88s result in about 180 rpm more than 4.56s at 70 mph with 35s and an 07-11 6 speed.

TJM12

I didn't realize the differences were so subtle. Makes me happy I chose 4:56 then, not much less performance but stronger gears.

planman

There are no widespread reports of failures of properly installed 5.13s or 4.88s. Strength would not be a concern unless you have a V8 engine swap and an extremely heavy rig.

You'd be surprised of the increase in performance on the highway from a couple hundred engine rpm. Of course, the performance difference off road of lower gears is significant.

I'm sure 4.56s are fine for your application, but lower gears result in increased performance without a reduction in strength that has resulted in significant failures in JK axles during the last 7 years.

rsbmg

This statement is confusing me a little I just want to make sure I'm reading it correctly.

1. Lower Gears result in increased performance.
2. Lower gears do not result in any weakness in the ring and pinion.
3. Are you saying there HAVE been significant failures with JK axles, but thats not because of lower gears?