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Please Settle This: Gear Ratio For 31's

M

M4Madness

NAXJA Forum User
Location
Springville, Indiana
First, I've read the tacked FAQ and read through 34 pages of topics that came up when I searched for "gear".

I have a 1996 Cherokee Sport. It has a 4.0L engine, an automatic OD transmission, and 3.55 gears. I'm wanting to lift it and install 31's. It is my daily driver, with most driving at highway speed. From my calculations, to get back to the stock gear ratio after adding the bigger tires, I'll need 4.11's.

Some say that I'll be happy with 4.11's, while others say to definitely go with 4.56's. I'm leaning towards the 4.56's, but want to be sure that I won't be disappointed -- some say that this is too low-geared for 31's.

Hopefully this can put the argument to rest, and future newbies will benefit from the input. Thanks.
 
Last edited:
This is like asking which is better, blonds or brunettes.
If you do a lot of highway miles, go with a lower numerical gear, ie. 4.10
If most of your driving is around town, the 4.56's will be nice.

Jeeps came stock with gear ratios from low to high. Many around here came stock with 4.56 gears on standard sized tires. My personal preference would be 4.56 for mixed driving.
 
I never exceed 60 MPH. According to charts I've seen, with 4.56 gears and 31" tires, I'd be running 2,410 RPM's. I tested my XJ on the highway today, and I turn about 2,300 RPM's in 3rd gear at 55 MPH. It didn't seem to be revving too high to me. If I can do around the same RPM's at 60 MPH in OD with 4.56's, I'd be satisfied. I seldom travel more than 25 miles on the highway at a time, but do travel 10 miles one way to work daily.
 
And, as I implied in your other thread earlier today, the likelyhood of you always running 31's is pretty slim.
 
mid-upper 2K RPM is the ideal band for best economy.

This link is helpful to decide but like others have mentioned, chances are you may want to go to 32s or 33s in the future unless you are very solid on staying at 31s
 
You can run any gear ratio with 31s!! They're 31s, practically stock! Who cares. Maybe not 3.07s, but 3.54s, 3.73s are FINE FINE FINE!

4.56s w/ 31s, are you kidding me! What a waste of time and money!
Leave your gearing stock with 31s, literally 2.5 inches taller than stock tires!!
People think too much about these Jeep ideal perfection figures.
235s - 30s - 31s - 32s - 33s - 34s - 35s
stock stk stk 4.10 4.10 4.10 4.56
4.56
 
XJEEPER said:
And, as I implied in your other thread earlier today, the likelyhood of you always running 31's is pretty slim.
Click to expand...

I don't do any offroad driving other than maybe driving a logging road during deer season. I'm just wanting to get a little more ground clearance for snow. I have absolutely no plans to go "all out" on this and have 35's under it or anything. This is my only transportation -- if it were a recreational mudder, I could see the possibility of going bigger one day.

barillms said:
4.56s w/ 31s, are you kidding me! What a waste of time and money!
Leave your gearing stock with 31s, literally 2.5 inches taller than stock tires!!
Click to expand...

From what I've read on this forum, stock 3.55's with 31" tires will cut thousands of miles life off my automatic transmission.
 
old_man said:
This is like asking which is better, blonds or brunettes.
Click to expand...

Red Heads I tell you, Red Heads!

Seriously he’s right though, it all depends on personal preference. I run 4.88 on 33” which most people will tell you are to low, but is right for me. Others like one of the posters above will tell you to run 4.10 with 33’s, which I can’t even imagine. Different strokes for different folks. If you are less concerned with highway cruising and fuel mileage go 4.55, if you are concerned with those things then 4.10 is what you want.
 
My 4.0 lost plentyof it's torque going fro 225X70 to 30X9.5 I would say going to 31 would be a dissapointment in the city. I wil be going 31 in the near future. 4.10 is the only way to go in my oppinion for a good responce both highway and city driving. 4.56 will put me too far up the RPM band. For crawling or mostly city driving then a lower gear ratio could be used.
 
I ran 31's and 3.73 didn't like it but I knew I was going to 33's so I didn't want to run 4.10's. I now have 4.56 and 33's and it's perfect. I can run 80 mph in overdrive most of the time. I like the stock RPM band, if I go to 35-36's then I'll be runing ~5.20 somethings. My gas Mpg didn't go down with the gears and tires but increased. The exhaust manifold leak hurts the mpg more then anything else. I get 14-15.

So if only 31's then I'd run 4.10's.
 
techno1154 said:
My 4.0 lost plentyof it's torque going fro 225X70 to 30X9.5 I would say going to 31 would be a dissapointment in the city. I wil be going 31 in the near future. 4.10 is the only way to go in my oppinion for a good responce both highway and city driving. 4.56 will put me too far up the RPM band. For crawling or mostly city driving then a lower gear ratio could be used.
Click to expand...


I am running 30x9.5's and was running 235/75/r15's before that. i didn't notice any drop in torque or other power loss. the 4.0 will still light up the mud tires i am running as i found out by accident the 1st time i got on it after getting the tires mounted. I also have the 5 speed tranny,so maybe that makes a difference.
 
M4Madness said:
I have a 1996 Cherokee Sport. It has a 4.0L engine, an automatic OD transmission, and 3.55 gears. I'm wanting to lift it and install 31's. It is my daily driver, with most driving at highway speed. From my calculations, to get back to the stock gear ratio after adding the bigger tires, I'll need 4.11's.
Click to expand...
That's correct. I put a 3" lift and LT245 75R16s on Moab wheels. Take offs from a Wrangler Rubicon. Also installed 4:11 gears front and rear and a TruTrack LSD in the rear Dana 35.

I loved LOVED that set up and probably would never have changed if I had not won a new Dana 44, new gears, new chrome molly axle shafts. I locked up both ends and went to LT285 tires.


Some say that I'll be happy with 4.11's, while others say to definitely go with 4.56's. I'm leaning towards the 4.56's, but want to be sure that I won't be disappointed -- some say that this is too low-geared for 31's.
Click to expand...
For a couple of weeks before the new tires were installed, I was driving on the 4:56 gears and the 245 tires. Hated that. Especially at freeway speeds. And talk about sucking gasoline. Oh my GOD!!!


Hopefully this can put the argument to rest, and future newbies will benefit from the input. Thanks.
Click to expand...
Nah. Just more opinions to add to the confusion.
 
PolishX said:
if he only "wheels" once a year to deer hunt then why is he here I ask the question?
Click to expand...

So, by your reasoning, only "hardcore" XJ owners should be here? I want to get a little larger tire under my Cherokee, and want to do it the right way. I was told that this site had the most knowlegeable members. Perhaps those who believe that are wrong.

Everyone has something that they go "all out" on. My interest that I spare no expense on is firearms. I own a $13,000 registered M16 (machinegun), various weapons with silencers, and a .50 BMG Barrett rifle. I enjoy these things and put most of my spare cash into expanding this collection. But I sure as hell don't look down on those who only own a .22LR. I try to help them out with their questions and get them interested in the sport. I don't adopt an elitist attitude and drive them away.

Anyway, thanks to those who have offered sincere advice. :wave1:
 
My take on 3.55 gearing, and 31's is. It sucks in town. with the A/C on you have hardly any power unless you just plain put it to the floor! My in town millage is horrible I'm talking from my worst 6mpg (was hauling three others to work for a week) to 10mpg what I usually average for a tank of city driving.
Out on the freeway it's not to bad as long as the road stays relatively flat. If it gets hilly you had mite as well put it in 3rd 'cause it's going to hunt for gears if you don't. IIRC I was averaging around 19mpg on long trips (I have a roof rack, and other wind catching/weight increasing accessories now). If I was in your shoes, and I was for sure I'm not going any bigger then 4.10 seems decent, but if you have any thought that you might want to run anything bigger than 31's then go 4.56.
 
:passgas: I have a 5 spd with 3.07s and 31s. Its a little different, but not much. I still get good gas mileage, just not 20 mpg like I used to on 205s. With a manual that comes stock with 3.55 gears it should be even better than mine, but I think your first guess is correct 4.10s would be good. Probably even a little more power than stock. If it was me I wouldn't even regear it unless you are Mr. Moneybags. Hell you can pick up cherokee axles at the junkyard from a 4 cyl with 4.10s and save a bunch of $$$. Thats what im gonna do except with an 8.8 rear and 35 inch tires!!
-Patrick
 
Stop and think that the charts are based on 1:1 ratio's in a manuel tranny. and the 31's will be a little wider increasing rolling resistance. The taller stance will increase wind resistance. Milage will drop slightly even if you regear. I say do a budget boost and get a set of trail tires for your hunting trips. a used set will cost half of what regearing will.
 
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