ok so my wife is wanting to put bigger tires on her XJ after we get the motor lined out. it's got 215/75-15's on it now and (i believe) 3.55 gears. i know it will need to be regeared, and from the research i did, it looks like going from a roughly 27" tall tire to a 31" tall tire, 4.10's will put us nearly back to stock overall gear ratio. this correct?

not worried about gearing it low, this is just her daily driver that she SAYS will get offroaded, but i dont think she will ever take it offroad, she just likes the look of a lifted XJ with 31's... it's already got a 3" BB, now we just have to get the tires.

 

You are correct. 4.10's with 31's will put your back to factory ratio.

 

awesome, i have a set of factory d30 4.10's i pulled out of my 86 XJ when i junked it and we are planning on swapping the d35 out for an explorer 8.8, so i will just hunt one up with tracloc and 4.10's