Poor Gas mileage? 31s and 3.55s... I don't know where to start.

[Mudderoy]

i'm running 32's with stock gears...gas mileage sucks too.....was considering a warn front hub conversion so as not to push the front end all the time....figured i'd definitely get an increase in gas mileage...and with the cost of gas the increased mileage would save me $$ essentially paying for the conversion....does anyone have any numbers on increaded mileage with these conversions?? maybe a new post is in order here...

I've been told re-gear and/or oxygen sensors. I re-geared Monday. Gas mileage seems to be much better, but I haven't run them long enough to be able to tell.

Oxygen sensor is next.

10.5 mpg with 32" tires 3:55 gears driving "MY WAY". 12.9 mpg 32" tires and 3:55 gears driving easy. Best guess after the 4:56 install LOOKS like 14.5 mpg. All of these are city numbers. That 14.5 mpg is 45 miles on 3:55 and 85 miles on the 4:56. Confused? In other words I think the 14.5 is going to be low. I'm guessing 16 mpg. This would be a 5.5 mile per gallon increase!

 

[SNOWBLIND]

sounds good...i know my exhaust is toast, so that is on this list to upgrade and figured i'd do an intake too.....hopefully will aid in mileage...i was suffering from a check engine light poping, so took to my buddies house who has scanner program...gas cap problems...wondering if this was a mileage issue too....but also figured that with over 120k on the ticker it is time to do exhaust and O2 sensor....now to pick out an exhaust and intake system!!

 

[MPETESS10]

all of this is why I really have no intention of goin bigger than the 30's and 2" BB I have now. maybe 31's with more lift and 4.10's. but alas
my 5spd and 3.07's on 30s gets me anywhere from 15-17 around town and driving "normal" I get between 21-24 hwy. if I drive sane I have gotten 25+mpg a couple times.

I do plan on upgrading to 3.55's eventually just for a little bit of help. it wont be much but anything HAS to be better than the 3.07's and with such a small jump I dont expect my mpg to change at all if anything I think it may get a little better especially around town.

goin from 3.08's to 3.42's was the best mod I ever did to my 2wd V6 S10 and its HEAVIER than my XJ

 

[winkosmosis]

Hey, you guys are talking about changing gears like it's nothing. How much are you all paying to get it done? Or are you all just that good that you do it yourself?

A well recommended off road shop here in Houston quoted me $1900 in labor for both axles...

 

[MPETESS10]

easiest way to swap gears is find junkyard axles wit the gears you want already in em. generally speaking most want or will at least settle for 4.10's unless you have over 33's. if your really lucky you might find the rare-est of the rare factory 4.56 equipped XJ although chances are the rear in thkis rare bird will almost surely be a D35. swapping complete axles can be done a couple hours even with hand tools.
I did it on the rear of my S10 by myself at work 2 hours a night until we closed and it took 3 days= 6 hours
this was all done on the floor with only floor jacks and jack stands and the first night essentially just getting ready jacking the truck up takin tires off and preparing. if I had to do it start to finish in 1 session I could pribably do it again in a matter of 3 hours or less.

if you take the shafts out and remove the brake backing plates with the brakes, lines, and e-brake cables still attached its litterally a 1 man operation. once you have the brake plates off all you do is remove the driveshaft and the ubolts and drop the axle housing out.

the front is just as easy remove brakes and driveshaft and unbolt all the control arms and the sway bar and drop the axle out.

its really a just a saturday operation to regear with junkyard axles if you find what you want

 

[Mudderoy]

Hey, you guys are talking about changing gears like it's nothing. How much are you all paying to get it done? Or are you all just that good that you do it yourself?

A well recommended off road shop here in Houston quoted me $1900 in labor for both axles...

I just had my gears swapped from 3:55 to 4:56, I paid much less than that. Actually any of the work I haven't done on my XJ this guy has. He has a 40's era gas station location. He does great detailed work, and he's hard to get a hold of because he's always so busy.

Falcon Auto

He is a close friend of my wife's side of the family. Just tell him Tony referred you. His shop is near I-10 and 45.

 

[winkosmosis]

Thanks for the tip, I'll check out Falcon Auto.

 

[m0n3ym1k3y]

not tryin to hi-jack or nothin but......

Wow ..... overload...anyways i got 31's assuming 3.55 cuz i cant find where it says ...oh its a 89 waggy limited 3 inch lift I6 and AW4 . So its running like crap , obviously too rich becasue i have the lil black ring around my exhaust tip. I claened out the fuel injectorss with a can on a pressure gauge thing that my dad has. ive checked the compression and the plugs were surprisingly clean. reset the tps and cleaned egr and iac. The next thing i was thinkin was O2 sensor, but i dont have 55 bucks two blow out my A$$ if im wrong.

 

[Jeepm@n]

i'm running 32's with stock gears...gas mileage sucks too.....was considering a warn front hub conversion so as not to push the front end all the time....figured i'd definitely get an increase in gas mileage...and with the cost of gas the increased mileage would save me $$ essentially paying for the conversion....does anyone have any numbers on increaded mileage with these conversions?? maybe a new post is in order here...

Spend you money elsewhere. I have the Warn kit and did not get any better then .5 miles to the gallon. I bought it for getting better MPG. Although now if I wheel it and one breaks it's alot easier to fix on the trail.

 

[live24wheel]

Hey, you guys are talking about changing gears like it's nothing. How much are you all paying to get it done? Or are you all just that good that you do it yourself?

A well recommended off road shop here in Houston quoted me $1900 in labor for both axles...

WOW! I have two different people here in Phoenix, 1 of them will install the gears and 2 ARB's for 500 total and one just charges a flat rate no matter what per axle of $250. Talk to the guys at the shops that do the gearing.... On the side....

 

[rjstiles]

How do you regear? If I do regear do I also have to do the front drive as well? What do gear ratio you recommend for the best fuel mileage?

 

[Mudderoy]

You have to change out the ring in pinion in the differencial. You MUST change both front and back, unless you remove the driveshaft from the front differencial. I'd never tried it so I assume that it would work. If you have a 4x2 then you only have the change the rear diff. Some people find replacement front and rear units with 4:10 or the rare 4:56's from the factory (OEM). This would be an entire swap of the complete unit not just the ring and pinion.

http://jeeptalk.org/gear_chart.php

Well this chart says 4:10 or 4:27. I'd seriously consider the 4:56. Get some feedback on people with 32" tires first though.

 

[Mudderoy]

Just regeared today, I'll let you know.

Was getting 10.5 city. Started driving easy, got it up to 12.9.

Next step will be the O2 sensors.

Ok just finished a full tank. 18.3 gallons, 238.5 miles, for 13.032 mpg city.

Sucks and sucks and sucks, and then it sucks!