NOTE: Inspection and replacement should be performed any time a problem is observed or suspected. Severe usage conditions may require shorter intervals — refer to the owner's manual for your truck.
The fluid level must be checked every 30,000 miles (48,000 km) on conventional differentials. On limited slip units, change the fluid every 30,000 miles (48,000 km). To check the fluid level, first make sure the wheels are chocked and then simply remove the plug from the side of the unit. Place a drain pan under the drain and fill plugs to catch any spillage. It may be necessary to raise and support the vehicle on jackstands to access the drain and fill plugs on the differential unit. If the fluid runs out or you can feel with your finger that it's not more than 1⁄4 inch (6mm) below the level of the hole, the level is satisfactory. Otherwise, add the following specified fluid with a syringe-like device you can buy at a local auto parts store.
For the limited slip differential use Hypoid gear Mitsubishi genuine gear oil part number 8149630EX or equivalent. For the conventional axle, the API classification is GL-5 or higher, and viscosity recommendations are as follows: