Sargejk

At (a hard-to-reach) 70-mph, my ’09 JKU automatic w/3.73’s is taching about 1,800 RPM in overdrive on 33-inch Procomp 305’s. The RPM’s jump to 2,800 with the overdrive turned off.

My biggest complaint is on highways and how the transmission is always dropping out of OD on even the slightest incline. I’m forever turning off the OD. The motor really spins, but at least I get some throttle response.

According to the Gear chart, looks like the 70-mph sweet spot is between 2,400 and 2,500 running 4.88 or 5.13 gears, respectively. I’m strongly considering 5.13 which would work for 33’s or 35’s.

Before I make the commitment, I’m anxious to learn what regrets I may encounter. Will my 15-mpg average mileage suffer, improve, or stay about the same? Will I still lack highway throttle response? Will there be differential whine? Will I still find myself turning off the OD? What else should I expect? I’m sure I’d enjoy the off-road gear reduction.

Would welcome your experiences.

Firelyle

2010 Auto 35's and 5.13 gearing. No complaints at all. It spins about 2300 at ~75 and the overdrive doesn't do the hokey pokey anymore. I didn't really notice any change in mpg's but then again it's a rolling brick. I know the r&p is small on the 5.13's but I have had no issues wheeling and we have a few rocks here in Colo. I just go easy on the gas and all has been good. Good luck with your decision!

Sargejk

Thanks....sounds encouraging! Hate the OD hokey pokey

familytime

We have an '07 with 4.88's,auto. if you're after gas mileage you need to keep it under 60mph for best mileage,anything higher your mileage will suck bad.With our current set up running 37's we still avg.17-18 mpg

Sargejk

So, 4.88 may be the better compromise between mileage and throttle drivability?

janders82

2010 JKU. Debated the same thing. All I can say is that i would have definitely regretted 4.88s...Go with the 5.13s and don't look back!

Btw, I'm running around 2600rpm at 70mph on my GPS, but I'm on 33's. another thing you may want to pick up if you haven't already is the AEV ProCal to reset your computer to your gear and tire size

rays0852

If you are going to wheel much I would strongly recommend you consider staying with 4.88 as the ring gear is so small at 5.13. Just sayin.

familytime

It's all going to be up to you,follow the gear chart and build your rig for what you want.Think about what max tire you want.Everyone will give you different feed backs.One thing i know about 5.13's is that you're getting a little thin on the ring,so if you wheel hard just be careful,if not you'll be fine

Maertz

Depending on the axle.... And tranny....

loonies

2010 Auto with 35's and 5.38 gearing...12000 miles since the regear. It is hands down the best mod I have done. I actually like driving the Jeep again.