UnbendingWings

How bad of an idea is this? Please tell me before I set sail to the islands of retard.

DenimDean

MirageMobile

AW4 or AX-15

scottmphoto

It's a bit low for 31's. 4.10's would get you better mileage and put you in the stock range. A lot of people (including me) run 31's with 3.55's.

Rock Toy

It depends on what you are planning to do with your Cherokee. If you are going to use it for a DD and weekend toy you may want 4.10s or 3.73s. If you are going to use it as mostly a toy the 4.56s would be OK.

Don't pay any attention to the Chart above it is for a manual with a 1.1 transmission ratio, as in a 5 speed in 4th gear.

Instead use this gear ratio calculator.

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

srb531

it will really jump when you punch the gas, and suck more gas then 4.10 will.

Outlaw Star

Simple math formula (Yes Math!, that stuff you kids thought you'd never put to use in reality. Lol) Old Tire Diameter/New Tire Diameter x Current Gear Ratio (tire size must be in inches for formula to work, just convert metric size to inches) = Effective Gear Ratio (This is what you vehicle is acting like it has with your selected tire size) Now the trick is to plug in different gear ratios into the Current Gear Ratio spot untill the final product comes the closest to the stock ratio (3.55 for Autos and 3.07 for Standard) This will give you the best compromise between power and fuel economy by making your vehicle think its still turning the stock size tires.

jsohway

I'm looking to upgrade my gears, I'm running 33s with the stock 3.55 gears. I just can't decide what I should put in yet

Outlaw Star

You should be fine with 4.56 gears. Usually the math works out to 4.10 for 31's, 4.56 for 33's and 4.88 for 35's

jsohway

Ok, I may just go with 4.88 since I plan on putting 35s on when the 33s are worn down. Thanks for the advice

Tom95YJ

This is correct when I regear I'm going to 4:56 even with my 35's because the 4.88 pinion is tiny on a d30

dogger15

Highway driving going 65+ you will run higher RPMs. Id say its a bit much for that. For city driving you will be fine. If you plan on ever going larger than 31s then Id go 4.56. My friend had 31s and 4.10s. He thought it wasn't enough for when he loaded up his xj with camping gear and wished he went 4.56s.

RubberSideUp

Having owned and driven XJs with 4.56s and 31s (both manual and auto trans equipped), I can tell you that 31s or 32s with 4.56 is about perfect in the real world. On paper people will say 4.10s, but I had 4.10s before 4.56s with 31s and the 4.56s provided much better acceleration and improved mpg. It was also much more fun to drive and towing was less problematic.

Fred/N0AZZ

Yes it will pull better under load and as far as the MPG goes you won't find that much of an increase over the 4.10's. IMHO the 4.56's would be a good choice just in case you decide to go with 33's in the future, plans do change. I run 4.56's with 33's and wish I had gone with 4.88's I'm thinking 35's with a long arm kit.

SteveMongr

Thank you for a great formula! And it's simple.