Use Dexron automatic transmission fluid for refilling or adding fluid to all transfer cases except the Sorg-Warner model 13-59, which is a run-dry unit and contains no fluid. To check the fluid level, position the vehicle on level ground and remove the transfer case fill plug located on the rear of the transfer case; the fluid level should be up to the fill hole. If lubricant does not run out when the plug is removed, add lubricant until it does, then install the fill plug. It is recommended to change the transfer case fluid every 60,000 miles (96,000 km), or sooner if the truck has been driven in deep water. Warming the fluid by driving 15-20 miles on the highway before draining will help it flow better and remove more contaminants. To drain and refill, drive the vehicle to ensure the fluid is at normal operating temperature, then securely raise and support the vehicle on jack stands. Place a drain pan under the transfer case housing below the drain plug, ensuring it is positioned to catch the fluid as it flows outward. Remove the fill plug before the drain plug to avoid complications, then allow the fluid to drain completely. Once drained, install the drain plug securely, fill the transfer case to the proper level with the required fluid, reinstall the filler plug, and finally remove the jack stands to lower the vehicle.