I just bought a 99 Sport and was wondering if there was a way to check the gear ratio such as a build code?

 

If you're lucky, the tags will still be on one of your axles. They should give you the gear ratio.
If not, you can go to a local dealer, give them your VIN and a couple bucks, and they can send you a build sheet for your jeep.
I don't know if they still do it, but you used to be able to email JEEP directly and get the build sheet for free. I heard that they did away with that, though. Could still be worth a try.

Keep in mind, since you aren't the origianl owner, it is possible that someone may have changed the gear ratio, for whatever reason, already.
If it's still stock otherwise, there's less of a chance, but you never know.
The only absolute, sure fire way to know, is to open up the dif and count the teeth.

 

Black Thunder if you can describe your Jeep and it is still stock we can help you with likely gear ratios. But to have to guess at the year and engine/transmission would be a lot of guessing.

 

It is a 1999 with a 4.0/automatic.

 

Most likely it's 3.55 then, as long as it hasn't been changed, or came with a towing package.

 

Towing package will have a hitch and a cooler for the tranny in front of the radiator. If it has that then you could have 3.73:1 or even 4.10:1 ratios but they are kinda rare.
Did you look for the little tag in the rear or front axles?

 

My jeep has the towing package and came with 3.55 gears..

 

 

The bottom center bolt has a 3.5. I assume that would make it a 3.55?

 

you have 3.55's

 

Like a majority of Cherokee owners. Some of us want different ratios and some have already changed their ratios but not many are ever happy with their current ratios.

 

Thanks for making this easy. Just trying to decide how big of tires, lift I can put on now without bogging it down too much. Thanks!