Auto 4.88s MPG before and after????
JK Enthusiast
Joined: Jul 2009
Posts: 321
Likes: 0
From: Tampa, Florida
If I could do it again I'd go with 5:13's. Im running 4:88's with 34" Nittos, the gas mileage is 17 plus on the Hwy 75 mph or so. 2011 Sport Hardtop, 3" lift Auto. I really think the lower gears would help out on the longer grades, mine still hunts around, even with OD off. My mileage was basted on Interstate travel. Around City/Hwy it's usually around 14 mpg. Also the lower gears could help out with possible Larger Tires in the future.
JK Freak
Joined: Jun 2011
Posts: 598
Likes: 1
From: Little Rock
Listen to Plan Man. He is telling the facts.
Many members of this forum will tell you that the "best" is whatever they have.
Here, this is not the case. He is giving solid advice on regearing an AUTO - which is not what he drives, so he has no reason to pridefully push the same decisions he made for himself. He is trying to help you out.
Many members of this forum will tell you that the "best" is whatever they have.
Here, this is not the case. He is giving solid advice on regearing an AUTO - which is not what he drives, so he has no reason to pridefully push the same decisions he made for himself. He is trying to help you out.
JK Freak
Joined: Jul 2011
Posts: 717
Likes: 0
From: Independence and Lexington, KY (depends on the time of year)
Originally Posted by planman
Because of aerodynamics and the mountains/hills you encounter driving to Tahoe, you aren't going to get great mpg at 75 mph regardless of gearing.
If you gear 4.88s, your fuel economy will be about 10-13 mpg at 75 mph to Tahoe because your transmission will be hunting between 3rd and 4th when you hit hills/mountains/crosswind.
If you gear to 5.13s, your fuel economy will be better because it will downshift less.
Your best fuel economy with an automatic would be with 5.38s, because it would downshift less.
If you were in Florida, with no hills or crosswinds, then the answer might be different, but not living in SoCal and driving the hills and mountains of CA.
If you look at the worksheet above:
5.13s with an automatic and 35s that are short and measure actual size 33s, at 70 mph, your rpms would be 2524--no where close to 3k rpm.
If I drive my 2 dr 6 spd at 3k rpm through the mountains for 800 miles between Billings, MT, and Moab, UT, my fuel economy is 14-15 mpg. 3k rpm does not equate to 8 mpg.
This is simple math and physics--not speculation or opinion.
If you are concerned about fuel economy, do your build as light as possible, stay at 70 mph or less, run the lightest combination of tires/wheels you can for a given tire size, run your tires at higher psi, run a Superchips Flashpaq program, and when you get to long mountain hills, turn off your OD near the base of the hill--it is better to do a long steep hill in 3rd gear with the OD off than to allow your transmission to "hunt."
Don't run a rack or exterior lights, or anything else that messes with aerodynamics.
Also, a Sprintbooster should help improve fuel economy because it reduces the lag in shift between gears when the transmission downshifts.
Heavy tires/wheels can lose you 1-3 mpg--maybe more if the tread is very aggressive and the tire psi is off.
A rack, with large lights can lose you 1-2 mpg.
Heavy armor and bumpers can lose you 1-2 mpg.
Tranny hunting can lose you 3-4+ mpg.
For a long highway trip, removing your front driveshaft or having manually locking front hubs can gain you 1-3 mpg.
35's with 5.13's
JK Super Freak
Joined: Mar 2011
Posts: 1,934
Likes: 2
From: Seattle, WA
Mine is an auto with 4.10s
As I read these threads about regearing my doubts only increase about the trade off, or return on the investment. It seems the cost to do it right (reputable shop + good quality products) can easily go over $1,500. Considering the gas savings we would have to drive a lot to pay the investment off.
On the other hand, it seems that regearing's justification lays more on the "rock climbing" ability or the very personal pleasure (=gratification) of having a more responsive Jeep.
Decisions, decisions...
As I read these threads about regearing my doubts only increase about the trade off, or return on the investment. It seems the cost to do it right (reputable shop + good quality products) can easily go over $1,500. Considering the gas savings we would have to drive a lot to pay the investment off.
On the other hand, it seems that regearing's justification lays more on the "rock climbing" ability or the very personal pleasure (=gratification) of having a more responsive Jeep.
Decisions, decisions...
Last edited by Sahara_Maverick; Nov 29, 2011 at 06:32 PM.
Thread Starter
JK Freak
Joined: Aug 2011
Posts: 834
Likes: 0
From: Long Beach CA
ok so..... I got my jeep back from Off Road EVO last night. $999 for gears and instal, you literally can not beat that. They are great with customer service and had my jeep back in half the time expected. Went with the 5.13s from 3.73s on 35s.
Here are my initial thoughts;
It's not some huge crazy difference that makes the jeep feel like a completely different car. It does make it feel very close to stock and maybe slightly better. I'm not supposed to take the jeep above 60mph till 100 mile break in period for the gears, so my MPG increase is relative. But for those wondering, mpg went from 14-15.5 to 18-19.5 which is a combination of streets and highway. Again, this is under 60mph.
There is a definite feel of ease during acceleration and passing. On ramps aren't something to dread anymore, and I'm not pressing my foot to the floor waiting for it to shift.
DOWNSIDE (and this may be purely a personal feel) I feel like the jeep wants another gear at top end. This also makes it louder inside the cabin because top gear is now at a higher RPM, but I do have a cat back exhaust.
I still would recommend 5.13s to anyone with 3.73s on 35s, and I would HIGHLY recommend Off Road EVO.
Any questions??
Here are my initial thoughts;
It's not some huge crazy difference that makes the jeep feel like a completely different car. It does make it feel very close to stock and maybe slightly better. I'm not supposed to take the jeep above 60mph till 100 mile break in period for the gears, so my MPG increase is relative. But for those wondering, mpg went from 14-15.5 to 18-19.5 which is a combination of streets and highway. Again, this is under 60mph.
There is a definite feel of ease during acceleration and passing. On ramps aren't something to dread anymore, and I'm not pressing my foot to the floor waiting for it to shift.
DOWNSIDE (and this may be purely a personal feel) I feel like the jeep wants another gear at top end. This also makes it louder inside the cabin because top gear is now at a higher RPM, but I do have a cat back exhaust.
I still would recommend 5.13s to anyone with 3.73s on 35s, and I would HIGHLY recommend Off Road EVO.
Any questions??
JK Freak
Joined: Jan 2010
Posts: 726
Likes: 0
From: Charlotte, NC
I'm getting ready to run 5.13's with 33'' tires 
. I'll let you all know how it handles in a few weeks after they go in. I'm used to driving 5+ hours at 3k RPM's every time I go home (Full time O/D Disabled), so even with the 5.13's, I will be turning at lower RPM's.
For what it's worth, I got 16 mpg driving at 70 for 3 hours turning 2900-3000 RPM's last week. That's 33'' Duratracs, and auto, and 3.73 gears.
. I'll let you all know how it handles in a few weeks after they go in. I'm used to driving 5+ hours at 3k RPM's every time I go home (Full time O/D Disabled), so even with the 5.13's, I will be turning at lower RPM's. For what it's worth, I got 16 mpg driving at 70 for 3 hours turning 2900-3000 RPM's last week. That's 33'' Duratracs, and auto, and 3.73 gears.
JK Enthusiast
Joined: Oct 2011
Posts: 165
Likes: 0
From: Littlestown,Pa
I drive 120 mile round trip 7 times every 2 weeks for work. It's all highway with hills. I set cruise control at 70 mph. With 33" tires, 5.13 gears, and a superchip I am getting 17 mpg. I am adding 35's and steel wheels next week so I'll update what I get them but I love the 5.13. No regrets at all.