lopezdist

Hi all had Drew formerly from Avalanche Engering now at BS Fab in Bayfield co do mine, 08 running 315 75 16, we decided to go with 5.13, while he had my jeep went to full Detroit in rear and lock rite up front. drove home to Farmington area and got 19.3 tach at about 1800 going 60, cant wait to hit Choke Cherry and really see what I can climb!! 5.13 gears are awesome, used my superchip to adjust accordingly, what a difference!! Would never change back to 3.73!!

CBrNoMore

This is akin to the bicycle analogy I was referring to in my earlier post. Less work the engine has to do = less gas consumption.

scottiebobbie

19 around town
22 hwy

CajunTiger

I am currently going through the same exhausting deal bro! I have some Yukon 4.88's sittin in my room waiting to install, but scared to due to my 2011 6 Speed manual buring gas. Its my daily driver and with paying child $1000.00 in child support every month, I gotta watch what I do. I am thinking about 4.10's and stay with my 33" Goodyears or 4.56's. I would LOVE to put the 4.88's and 35" tires, but scared of how much gas I will burn. Been having the gears for 6 months or so and still have not installed them.

planman

If you are concerned about fuel economy, wind resistance from speed, the weight of your rig, and the aggressiveness of your tires make way more difference than 4.88s with 35s will.

If you run lighter armor, lighter tires/wheels (maybe an AT or less aggressive MT, and drive slower, you'll get over 20 mpg at 55 mph, about 20 at 60, around 18-19 at 65, and around 16-17 at 70. If you drive 80 mph, your fuel economy will suck regardless of the gearing.

You'll need a tuner/programmer to adjust for tire size. The Superchips makes almost a full 1 mpg difference at 65 in our older JKs. I don't know what is available for the '11s.

JKs with lower gears (higher numerical) get better in town fuel mpg.

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JKRVEE

I've installed several sets of 4.56 gears in 2012 with 35"s, works great, 2400 rpm at 70, and I put 4.88s in the 12s with 37"s and the same great results. Mileage? We buy a brick shaped vehicle for mileage? I couldn't even tell you what my 08 JKUR with 5.38s and 40" MTRs gets.

CajunTiger

I drive my Jeep on the interstate, so at least 70mph is what I drive. I actually drive 65 since I can't use 6th gear at all, just to save some gas. Thats mainly done when I go to work and back every week cause there is nobody on the roads that early in the morning and I don't have to worry about gettin run over...lol. But when it comes to running with the traffic, driving 65 on the interstate can get scarey.
So I guess what your saying is that I should be OK with 4.88's and 35's? I don't ever look at driving 80 mph in my Jeep, but if I wanna run with the pack, 75 would be nice, knowing my milleage will suffer, but just knowing I can when I want is fine with me. I am so tired of trying to decide what to do it drives me crazy! I normally drive 70, but when I get in from offshore, I kinda wanna get home a little faster if ya know what I mean...lol My profile has everything I have put on it. Front and rear bumpers came out to about 200lbs more, a winch is coming soon.

TURTLECON

I just swapped in 4.88s. 2008 JKU auto 3" lift 35s and at 70mph on freeway I'm just under 2500rpm. Drives fine. If I slow down and cruise at 65mph I'm at 1500rpm which is fine by me. I'm not in a rush.

planman

75 will be fine, but depending on hills and wind, you are likely looking at 15-16 mpg.


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JPB

ok so let me see if i can sum up all of this info. and please correct me if i'm wrong.

1. If I ever plan to put 37's on this jeep, I should probably get the 4.88's.
2. I would probably get better MPG with 4.88 in town as opposed to 4.56.
3. 4.88's would cruise at higher RPM's on the Hwy (say at 75mph), but this is not so bad because of less strain on transmission/drivetrain and 200-300 RPM's higher doesnt really make that much of a difference.
4. Runnng 4.88's as opoosed to 4.56 on the Hwy at 70-75mph will not make much of a difference in MPG because of wind resistance, weight, tire/wheel setup, etc.

Are the answers to all of these statements yes for the most part..

Remember i'm pretty much on flat land, drive probably 90-95% in town, once in a blue moon go on a light to moderate trail (no rocks), mostly camping, fishing, and exploring type stuff.

I think i would "like" the 4.88 but I think for my purposes 4.56 will probably be the way I will go.... opinions happily accepted .Oh.. BTW are my statements correct?
Cheers