For 33" tires, 2.5L engine, and the 5-speed manual transmission, go right to 4.88. 4.56 is recommended for the larger 4.0L engine and 33" tires but for your 2.5L, 4.88 is the correct ratio. The D30 is fine with 4.88 gearing, I've been running 4.88 for 8 years with 35" tires and f/r lockers and the only thing I've broken up front on my Dana 30 was an axle shaft. 4.88 is the standard recommendation for 33" tires and the 2.5L... 4.56 is not enough gear for that engine and 33" tires. Trust me on this, the 2.5L engine needs those slightly higher rpms to perform well with that big of a tire.