tonkatoy89

i'm new to this jeep only had it for a year now i wanted to know if 31x10.5 r ok with the gear ratios 4.46 or can i go bigger i am putting on a RC 3"lift next week thank you for any info

eggdashure

Is that ratio supposed to be 4.56? I usually see guys run 33's on 4.56 and 31's on 4.10's. But, that's merely a general guideline, all depends on how you plan to drive it.

SeriousOffroad

4.56 are way too tall for a 31" tire, and your lift height has no bearing on gears.

www.grimmjeeper.com
Use the gear calculator.

kirknd4spd

Which engine and transmission do you have? I know with my 2.5 and 5 speed, when I regear it, I'm going straight to 4.88's, even with 31's. Simply because my stock 4.10's arent low enough for the 29" tires I have on it now.

salad

Stock gears can barely turn stock tires? Sounds like the 2.5L lol

kirknd4spd

Yeah, its tolerable on the road, but 5th gear is useless around town. It gets around ok, they just didnt gear these Jeeps anywhere near low enough stock (even the 4.0's, I dont like the 3.07's or 3.55's in XJs).

tonkatoy89

i have the straight 6 242 engine and its an automatic Aisin Warner (AW4) 4speed transmission and yes they are the 4.56s
i dont really understand what seriousoffroad said they were to tall for 31"tires
thanks for the info im sure i'll need alot of it lol

Outlaw Star

Also try this formula, Old tire diameter/New tire diameter x current gear ratio = effective gear ratio. This will tell you what gears your xj is "acting" like it has.

01mainexj

Serious was saying the 456 gear ratio is too low of a ratio for 31 and it'd be better with 410

Outlaw Star

Yes. 4.10 will be right for 31s w/auto transmission. With that ratio, your Xj will act like it did with stock 27" tires and 3.55 gears. Your engine won't have to rev as high to turn the tires. With 31s and the stock 3.55 gearing, your Xj thinks its got 3.07 gearing and the engine works harder to turn the tires.

tonkatoy89

ok thank's ya'll now i know what my next step is