[MOPWR2U]

Actually, I never said two vehicles should be turning the same RPM while going down the highway. What surprised me though, was that a Jeep that is made for street only and has a top speed of 160 mph is wound out more in high gear while driving the speed limit than a Jeep that is made for rock crawling. They do call it the "Rubicon" after all. I expected it to be the other way around, and that the rock crawling Jeep would be turning more RPM.

Why does an off road model like the Rubicon need a deeper overdrive in its transmission than a Jeep that goes 160 mph? Its not like the 3.8 V-6 isn't meant to rev a little bit. So why is the Rubicon (or any Wrangler for that matter) geared so tall on the highway?

Answer: C.A.F.E. ratings are more important than having gearing that would actually work better. I still say the Wrangler is geared too tall, even with stock tires.

 

[Scout]

I just installed 5.13s with 35 toyos MTs,I'm turning 2400 @70mph(GPS)with an auto.IMHO thats what the 3.8 needs to push that brick down the road.

 

[highoctane]

Why does Jeep gear these Wranglers so tall from the factory? The Rubi with its 4.10 gears is geared too tall for even the stock 32" tires. Our Rubi with stock gears and tires will turn 2200 RPM at 78 mph, while our Grand Cherokee also with stock gears and tires turns 2700 RPM at 78 mph. Both Jeeps were being driven on the same freeway at the same speed on the same day, my wife was following me in her Grand Cherokee and I called her on her cell phone and asked her how many RPM her Jeep was at.

So why does the RUBICON version of the Wrangler, which is supposed to be the ultimate top of the line OFF ROAD model of Jeep vehicle, have taller (effective) gears than a street only version of a Grand Cherokee? Come on Chrysler, figure it out. The Rubicon should have came with 4.88 gears for the 32" tires it comes with. Or, it shouldn't have such a deep overdrive in the transmission.

The effective top end gearing has absolutely nothing to do with trail performance unles your in 6th gear 4hi doing 70 mph on the trail. The Rubi has EXCELLENT low range gearing for crawling around on the trails, especially the 6 - speed. Your Rubi must be auto? My 6speed Rubi with stock gears and 35" Mud Grapplers is taching about 2500 at 80 in 6th. I drive 70mph in 5th and tach 2700. 6th gear at 70 is just about 2100-2200. The auto has a MUCH taller overdrive gear than the 6speed. Which is why the general recommendation for regearing a Rubi on 35s is 4.88 6-speed, 5.13 or even more preferably 5.38 for auto. For 37s 5.13 6-speed and def 5.38 for auto.

 

[MOPWR2U]

Agreed, the Rubi with its 4:1 low range works very well off road. Pretty certain everyone else was talking about high range gearing on the highway though, at least that is what I was talking about.

My Rubi is in the shop this weekend getting 5.38 gears installed. Thats why I'm sitting at home surfing the net, instead of out on the trail doing some exploring. I think the 5.38s will work well for the auto trans and 35" tires it will have .

 

[2k2wranglerx]

my question is what is the ACTUAL tire size you guys are running?

i've got 35" KM2's on a 17" rim and they measure like a large 33-34" tire.

i'm torn between 4.88's and 5.13's. it's my wife's jeep. 07 X with 4.10's, superchips, and the KM2's. it sees almost no trail time at all, it's all highway/mall crawling. highway is 75mph-80mph regularly in the AM commute.

if it was a true 35 i'd be all over the 5.13's, but these run small.

i'm torn between the 2.

 

[tkob1060]

my question is what is the ACTUAL tire size you guys are running?

i've got 35" KM2's on a 17" rim and they measure like a large 33-34" tire.

i'm torn between 4.88's and 5.13's. it's my wife's jeep. 07 X with 4.10's, superchips, and the KM2's. it sees almost no trail time at all, it's all highway/mall crawling. highway is 75mph-80mph regularly in the AM commute.

if it was a true 35 i'd be all over the 5.13's, but these run small.

i'm torn between the 2.

I've been running 35 KM2's for 70K miles with 5.13s and love the combo. I've done a TON of highway driving with them and cruise between 70-80 almost all of the time, you will still have some down shift on longer hills with cruise on, which makes me wonder what the 5.38's would be like. 4.88's IMO would be a waste.

 

[MarcusRTJ]

From all of the reading I've ever done the choice with an AUTOMATIC is 5.13s if you have D30/D44 and 5.38s if you have D44/D44 (Rubi).

I am going 5.13s in our 4 door auto when I regear it and put it back up on 35s sometime this year.

For comparison, I have a 6 speed two door on 35" MTRs (real 35s) that gets better mileage when I don't use 6th gear. It has 3.73s right now. 6th gear works, but it slugs ALOT.

 

[2k2wranglerx]

I've been running 35 KM2's for 70K miles with 5.13s and love the combo. I've done a TON of highway driving with them and cruise between 70-80 almost all of the time, you will still have some down shift on longer hills with cruise on, which makes me wonder what the 5.38's would be like. 4.88's IMO would be a waste.

and you have an auto right? i appreciate the input since you're running the same tires so i know they're the same size.

what RPM are you at around 70mph?

Thanks man

 

[tkob1060]

and you have an auto right? i appreciate the input since you're running the same tires so i know they're the same size.

what RPM are you at around 70mph?

Thanks man

yes auto and I run the superchips too.

I think I'm at 2400 at 70, and around 2600 at 75-80. I'll check tomorrow if I remember.

 

[2k2wranglerx]

yes auto and I run the superchips too.

I think I'm at 2400 at 70, and around 2600 at 75-80. I'll check tomorrow if I remember.

PERFECT! thanks man. that's right where i want her to be. I just don't want it spinning 3,000 rpm at 70 mph.

Everyone talks about what they've read... its super helpful to hear from someone with the same size tire. thanks man.

 

[jeepnick]

PERFECT! thanks man. that's right where i want her to be. I just don't want it spinning 3,000 rpm at 70 mph.

Everyone talks about what they've read... its super helpful to hear from someone with the same size tire. thanks man.

Glad I didn't listen to you guys when u tried to talk me into 5.38
I'm spinning 2850 at 70 (I'd give u the finger but I'm on tapatalk)

 

[2k2wranglerx]

Glad I didn't listen to you guys when u tried to talk me into 5.38
I'm spinning 2850 at 70 (I'd give u the finger but I'm on tapatalk)

Hey now, that was matt that tried to talk you into steeper gears! I was 100% non-commital

 

[reedjk]

i am going with a g2 5.13 gears in a 4 door with auto... 35's ...i got a killer deal from a guy who sold his jeep..brand new in boxes $200 for front and rear....
i think when you add winch+ bumper rear spare tire and bumper,rocksliders, jerry cans, hilift and mount,tool box, hardtop....cooler full of frosty beverages, camping gear, 1 fat girl or 3 skinny ones...it seems they are the best choice 5.13's. put it this way we just changed the weight to a surburban.
and with an added computer flasher of your choice to edit your tire size and gear ratio...you will be good.
great info on here nice chart
dont forget your gauge pod for your tranny temp
www.jkgaugepods.com

 

[ffa_nsk]

i love my 5.13 on 37's. i never reprogramed the computer/spedo and i dont see excessive downshifting except when going up a long steady hill. dont expect to go faster than 70 without realy givin it some gass. go with 5.13 you will love it