gears

i found a thread that said that if you want to have 30" or 31" tires you should have 4.10 gears! i have the diesel xj version for europe and the gears are 3.73. will there be a problem regarding gear change etc?

thanks

Well, I would strongly recommend 4.56 or even deeper. If you drive 27 tires (normally stock are around that):

3.73 -> 27"
X -> 31"

So X resolves to 4.28, so if you grow one step, it'll make not much of a difference; 4.56 will change driving marginally; a 4.88 would be best for off-road use, but you should calculate your max RPM for all your gears and see if the setup pleases you. I have an Excel sheet designed for AX15/AW4 transmissions and fuel engines; you could use it to make the proper calculations for your engine/transmission setup and decide for the best gears.

In my case, I'll never put tires bigger than 32" on my XJ, it came stock with 3.07 gears and I'm going to 4.10; I don't want to go deeper as I drive alot on the highway and 70mph is necessary for me, but I want good off-road performance.

If you're interested in the Excel sheet, PM me with an Email Address I can send it to.
Regards

3.73's are fine on a 4 cylinder with 31's so Id imagine youd be fine on your diesel rig.. Wait for a sure-fire answer tho.

I dont personaly see the need to regear unless going 4.56 or deeper...

I wouldn't worry about changing it unless you are going to crawl it. The difference isn't going to be that bad. You may need to change a speedo gear to get the speedometer right, but that is a piece of cake and fairly cheap. I* run 4:56 , but I have 35" tire and rock crawl it.

4.56 or deeper for 30' - 31's? What?

4.56's I would recomend for 33's at the least, to around a 35', which is what most people I know using 4.56's run. If you want a little more torque, like my friends with 36's, they are using 4.88's.

I run 32's on stock 3.55's for over a year, and, although I didn't have amazing gas mileage, it was still fine driving around town, and I still had a ton of power.

Begster, you should consider that a diesel engine works at lower revs than a gasoline engine, so if it comes stock with 3.73, you would mantain it stock with 4.28 gears and 31 tires; that's why I recommend 4.56; many people run 4.56 with gasoline engines and this way it's a really deep gearset, but on other setups it must be analyzed independently.