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Ugh... MPG

A

AdamGBabcock

NAXJA Forum User
Location
Puyallup, WA
I know I didn't sign up for fantastic gas mileage when getting a 4.0l with 35's (factory gears) but to me something seems off. Perhaps it's my math but what is your guys' average MPG? I filled up and calculated 7 :tear:

The ZJ I had on 35's got 9.8 for the 5k miles I put on it with 3.73 gears. I figured I'd do better with the inline 6 haha.
 
7mpg with 35" tires and 3.55 gears seams about right to me?
Time to re-gear!
 
when you calculate the mpg are you guys adding extra miles due to the over size tires?

whats really bad is im getting about 10 mpg on factory gears and tires
 
Not calculating the oversized tires... My speedo is roughly 22% off :laugh: so based on my rusty high-school mathmatics :banghead:that'd put me closer to 8.5mpg?(n)(n) Still not elated. What gears would be ideal for better gas mileage and not compromising and wheelability? :read:
 
4.10' seems to be a happy medium I ran 4.88's just fine.
 
I check my mileage with each tank full. With 35's and 4.88's I average around 16.5mpg daily driving each day, and usually around 19mpg on the highway depending on speed (seen as high as 21mpg). The last couple tanks have had trail miles on them so I haven't been able to get an accurate reading for a couple weeks. I also have a corrected speedo so I know this is pretty accurate within 1-2mph.

Make sure your motor is tuned up (plugs, air filter, etc), air pressure is correct, and your geared properly.

Also, if you need a gear calculator I prefer this one.

http://www.grimmjeeper.com/gears.html

You'll want 4.88's regardless though. I'd go deeper if I could.
 
TORX said:
I check my mileage with each tank full. With 35's and 4.88's I average around 16.5mpg daily driving each day, and usually around 19mpg on the highway depending on speed (seen as high as 21mpg). The last couple tanks have had trail miles on them so I haven't been able to get an accurate reading for a couple weeks. I also have a corrected speedo so I know this is pretty accurate within 1-2mph.

Make sure your motor is tuned up (plugs, air filter, etc), air pressure is correct, and your geared properly.

Also, if you need a gear calculator I prefer this one.

http://www.grimmjeeper.com/gears.html

You'll want 4.88's regardless though. I'd go deeper if I could.
Click to expand...

Why don't they make 5.13's for jeep axles? Is it a mechanical problem that they can't over come. Or just see no need for them.

Dave
 
you can go all the way to 5.89s in the 44. but the 30 is limited to 4.88s. with 35s, dual dana 44s and 5.13s would be more ideal. or 5.38s and a 37"+
 
Okay, I was already planning on tuning it up, replacing filters, and checking psi... The normal stuff. I looked online and saw I can get 4.88 ring and pinion sets for anywhere between $129 a set to $300+ a set. Anyone had any bad experiences with cheaper gears? Also, is this all I will need to change them or are there other parts involved? They both have to be done at the same time if I plan on putting it in 4wd right?
 
should get a master install kit as well
 
AdamGBabcock said:
I know I didn't sign up for fantastic gas mileage when getting a 4.0l with 35's (factory gears) but to me something seems off. Perhaps it's my math but what is your guys' average MPG? I filled up and calculated 7 :tear:

The ZJ I had on 35's got 9.8 for the 5k miles I put on it with 3.73 gears. I figured I'd do better with the inline 6 haha.
Click to expand...
that sounds low, (a) include the extra miles (just multiply odo difference reading by 35, then divide by 28 or so) (b) you probably have other issues like a bad upstream O2 sensor, thermostat stuck open, or temp sensor. It's still going to suck with stock gears of course.

ECKSJAY said:
mpg, haha
Click to expand...
seriously, how often does this come up? :rolleyes:

dan89XJ said:
You can get 5.38's for a LP D30 :)
Click to expand...
if you want it to break the carrier in half, chew teeth off the ring gear, and/or snap shafts like toothpicks, sure, that's a GREAT idea!

AdamGBabcock said:
Okay, I was already planning on tuning it up, replacing filters, and checking psi... The normal stuff. I looked online and saw I can get 4.88 ring and pinion sets for anywhere between $129 a set to $300+ a set. Anyone had any bad experiences with cheaper gears? Also, is this all I will need to change them or are there other parts involved? They both have to be done at the same time if I plan on putting it in 4wd right?
Click to expand...
you need a master install kit and yes, both have to be done at once to use 4wd. Installing gears is not for newbies, you will need a few hundred bucks in tools to do it as well, and plenty of patience. Search for a "how to set up gears" article.
 
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