Originally Posted by roy'sz

READ YOUR SERVICE MANUAL. Every 2 years you are supposed to change your diff fluid, if you have a manual trans oil is changed every 2yrs. Mileage on both is 24,000 interval. If you are really working trans and diff often as in tracking or spirited canyon carving, or stop and go traffic being that you aren't getting sufficient air flow across the cooling fins on the diff and trans then I would contemplate sooner. Coolant is also every 2 years as well as the Power steering.