Factory tow package provides two-row radiator (standard is one-row), auxilliary tranny cooler out in front of the radiator/ac condenser, synthetic gear oil in the rear dif to handle the extra heat, as well as hitch and wiring. You are on 31 inch tires and stock gearing- you will generate a lot more heat in the tranny than if you had stock 28" tires, and you will have lower rpms/less power. My bet: you cook the tranny, if you tow more than a few miles or over hills. You need 4.10 gears in the axles.