4:10's - AX15 - 31's 75-80mph in 4th @ 2200rpms. MPG are great speedo is dead on.

I have a lot of stop and go on hills in and around my town and it's been great. Towing is good as well.

 

somethings wrong with your numbers. 4.10's is overgeared for 31's

i run 4:10's with an ax15 on 32's and my speedo reads about 16% off

you should be runing around 3250 rpms in 4th gear at 75mph

and there is not a chance that your speedo is correct unless you changed to the correct speedo gear

 

4.10's on 31 is my dream setup
but thats a long way from here

whats mpg like?

im currently at about 17.5mpg and want to stay there

 

I've got a thing for jeeps with crappy mileage. Both my keeps get 13 mpg max and that's with plugs, wires, coil, air filter, injectors, yadayada.

 

That's true. I think when my speedo reads 75 i'm going about 65 which equates to about 15% off. At some point, i'll be replacing my speedo gear, however i'm going to wait until the 33s are on so i'm not doing it twice...

65mph for me gets has engine running at about 2500 or 2600 rpm (in overdrive for an AW4 auto).

 

Thank you!!!

I'm reading all this, thinking to myself that these people have to be nuts! My speedo is really off and I'm on the same setup. The faster I go, the more the.speedo is off.

 

The effective gear ratio with 31s running a 4.10 gear ratio is 3.57 which should be great for a DD with light wheeling.

27/31x4.10=3.57

 

If i keep the jeep i think 4.10s are in the near future then along with a bored tb and exhaust.

 

I can't get any better than 14 mpg even with a light foot, MSD plug wires, champion plugs, and a cleaned TB. I'm definitely looking into swapping in some 4.10s because i hate the mileage with gas prices the way they are. Plus I'd love to have more torque even though I can still spin the tires by hitting the gas lol

 

my cherokee has 31" bf a/t's and 4.10 gears. the chart shows it should be real close to the factory ratio. it is not. my gps shows me at 56 when the speedo says 65. but i like this setup. i have plenty of power. its around 2100 rpm at 55. i wouldn't want to drive over 75 for any distance though. maybe to pass someone. i haven't figured the mileage but i can see that its not terrible. i am guessing above 15 mpg and below 20 mpg. if you plan on pulling any type of trailer i think this would be a great setup. if i was going to get serious about crawling i would want some lower gears.

 

I'm going to bore the throttle body and get an exhaust and go from there. Most likely I will regear in the long-run I just haven't gotten the guts to spend over a grand on gears. 4.10s sound like a good choice when I do regear though.

 

Always keep your eyes peeled for 2.5L XJ part outs. That's how i got my 4.10s. Probably the best money i have spent on the jeep yet. Gave the guy $250 for both axles and took them out with a little help from some friends. Best part is the guy was only 15 minutes from my house. I think i found him on craigslist.

 

I did see a 4 cyl Cherokee for 500 bucks on craigslist a while back. Too bad that was while shopping for my current jeep rather than building it.

 

Id say if your jeep had 3.55s from the factory the speedo wouldn't be off much. But if you were lucky enough to get the great 3.07s id say its way off with 4.10s and 31s haha

 

I run 4.10s with 35s and its ok, got the axles already geared and its flat land forever around here. my speedo says 55 and im running 54, with an auto so suits me just fine. havent figuered out milage yet but i know it sucks!