I drive on 255/55 18's. I dont know exactly why I drive in 2wd only since it was that way when purchased. I jumped the check wires a while back and it indicated a problem with a control switch or unit or something under the tranny lever in the middle. I tested it in the dirt and sure enough that is exactly how it works. 2wd in 4H and 2 rear wheels lit up on the TOD display. 4LOW and I get 4LOW with all four wheels lit up on the TOD display. I've been driving it this way for a year or two and seems to have had no problems other than that dang blinking light. So I refinanced the house and now I can do some other things like put a turbo kit on my MR2 and try some new gears for the VX. I checked some sites and found that the ring/pinion is a 8.5 10 bolt as used on some other Jeep models and GM models. Man you guys ask alot of questions.