gear ratios

huskerdoc12 · #1 (**permalink**) 10-18-2005, 10:25 PM

I don't even have my jeep yet. "the Boss" a.k.a mrs. huskerdoc say I can get my toy in the spring. married guys know what i mean about "the boss". I am trying to learn as much as I can before I start shopping. How does the gear ratio affect the maximum allowable vehicle speed limit? I'll probably have more of a daily driver but i am sure i can find some nebraska snow drifts or fields to "play" in. I tried to find an easy to understand table on the web. I found equations instead. help please.

mingez · #2 (**permalink**) 10-18-2005, 10:58 PM

Well, a "taller" or "Higher" gear (lower number) means better top speed ability. But taller gears limit your torque and 0-60 generally considered bad for offroading. So, off the line, it's less power.

At higher speeds, a "lower" gear (higher number) is better for power and torque, but can limit your over all highway speeds and may wine do to more rotations and more gear surface contact. Most offroad enthusiasts seek to install lower gear ratios intended to increase off road performance.

So, for example, I lowered my gears from 3.73 to 4.56 in my XJ to increase torque, and accomidate the larger 33" tires I installed.

Here's a much more eloquent explanation:
http://www.webejeepin.com/Gears.htm

huskerdoc12 · #3 (**permalink**) 10-18-2005, 11:36 PM

can I assume that with 31'' tires a gear ratio of 3.73 would be fine forsome light off-roading and occasional interstate travel? I am looking at cjs for the spring. I will read the link. thanks.

Junkpile · #4 (**permalink**) 10-19-2005, 10:14 PM

The best performance oriented gear ratio for your jeep is going to be determined by several factors. Get the Jeep and then worry about it. If your main concern is the RPM the engine will be operating at in a certain gear and at a certain speed, use the charts.

Generally taller gears offer more topend speed, but only to a point. If you are trying to push a tall diff gear and the engine just doesn't have the balls to spin past 3000rpm in top gear, then going to a shorter gear that the engine can push easier might actually allow a higher top speed. Of course this usually comes at the price of accelerated engine wear and higher fuel consumption depending on driving style.

huskerdoc12 · #5 (**permalink**) 10-19-2005, 10:23 PM

thanks. the web site was very helpful

Bounty__Hunter · #6 (**permalink**) 10-21-2005, 10:33 AM

Quote:

Originally Posted by huskerdoc12

can I assume that with 31'' tires a gear ratio of 3.73 would be fine forsome light off-roading and occasional interstate travel? I am looking at cjs for the spring. I will read the link. thanks.

Yes, that's a good common combo for all-around use.

smell my dirty poodle · #7 (**permalink**) 02-01-2007, 10:33 PM

i have 31" tires & 4.10 diff gearing with an auto trans. low end power is sick. gets up to 2,900 @ 60 mph though.

jfrabat · #8 (**permalink**) 02-23-2007, 05:21 PM

I also have 4.10 on 31" Bridgestone Duelers HT (2.5L engine), and accelerating when you are in 5th at 55 mph or more is slow... But it does have acceptable acceleration (not enough for any kind of racing or anything, but more than enough for driving and offroading, which is fine for me; this IS a Jeep we are talking about, after all!).

Felipe

TwistedCopper · #9 (**permalink**) 02-23-2007, 08:26 PM

I ran 32's on an EFI YJ with the 2.5L. I was fine with it. A few mods made it more liveable.

montana_jeepn · #10 (**permalink**) 02-25-2007, 10:52 PM

I have 33's with 3.73 gears, 4.0, and 5spd.
I am seriously looking at going to 4.10's in hopes that she will drive similar to when I had the stock 30" tires on. I am also hoping to gain back a little gas mileage. Would there be any reason to go down to 4.56's? Thanks!

TwistedCopper · #11 (**permalink**) 02-25-2007, 11:55 PM

Quote:

Originally Posted by montana_jeepn

I have 33's with 3.73 gears, 4.0, and 5spd.
I am seriously looking at going to 4.10's in hopes that she will drive similar to when I had the stock 30" tires on. I am also hoping to gain back a little gas mileage. Would there be any reason to go down to 4.56's? Thanks!

I wouldn't re-gear for a tire that is one size larger than the stock size. It's a waste of money.

and

If you were to re-gear, the small difference between 3.73 and 4.10 gears would barely be noticeable.

jfrabat · #12 (**permalink**) 02-26-2007, 08:50 AM

4.56's will give you more torque. Perhaps your mpg will not be as good, but if you offroad often, it may be worth it. It all depends on what you want out of your Jeep. There are many sites (like http://www.quadratec.com/jeep_knowle...article-26.htm for example) that will give you a quick guide and should be used as a starting point.

Felipe

smell my dirty poodle · #13 (**permalink**) 04-02-2007, 10:20 PM

I run 4.10 with 31s and Im pretty happy. dont expect to save alot on gas though. Like that matters any way.

jfrabat · #14 (**permalink**) 04-03-2007, 11:41 AM

I run 31 on 4.10 also, but I have 4 angry squirels under the hood... Not TOO shabby, if you are not running drag or anything like that...

smell my dirty poodle · #15 (**permalink**) 04-04-2007, 01:00 AM

howd you know i dress in drag? get this my 46 cj2a has a four banger 5.85 gears and 28" stock tires climbs about any thing wont go over 50mph.

98XJ · #16 (**permalink**) 04-04-2007, 12:29 PM

Quote:

Originally Posted by smell my dirty poodle

i have 31" tires & 4.10 diff gearing with an auto trans. low end power is sick. gets up to 2,900 @ 60 mph though.

If you've got the AW4, you should be doing closer to 2100rpm at 60mph....unless you're leaving it in 3rd gear, then its ~2800rpm at that 60mph. Maybe your speedo was off when you read those. I would love 4.56's with 31's. Itd make it a beast and have 2300-2400rpms at 60-65mph.

98XJ · #17 (**permalink**) 04-04-2007, 12:31 PM

And on top of that, 4.10s with 31's would be comparable to stock with 225's. Not really "sick power" in my opinion unless your other car is a geo metro.