The previous owner put differnet gears in the rear of my truck, I dont know what they are but I know originally they were 3.73. I want to find out what gears are in the back so if I pop off the diff cover its that easy right? There isnt all kinds of oil or anything thatll come out or do I have to torque down the bolts or anything? I would think there would be the diff fluid or something but I dont really know awhole lot about these things. Its a 12 bolt btw. Also because of the np203 tcase I have, both axles are always powered. And because I have different gears in the front, if I go really really slow it'll pop and jerk a little. Thats why I really want to know what's in the rear so I can put the same up front. And also if I go from 33" tires to 35"s it would rev lower on the highway and I'd get worse mpg cause of the weight? I think thats what I've been told, because at freeway speed and without OD it revs pretty high right now.