Calculating your crawl ratio is quite simple. Just multiply the transmission gear and the transfercase, and axle ratio. For example if you have a 95 YJ with 4.56 gears, take 3.83 x 2.72 x 4.56 = 47.5. (3.83 AX15 1st Gear, 2.72 NP231 Low-Range, 4.56 Axle Ratio). So with that setup you would end up with a 47:1 crawl ratio.