Diagnosis of Locking Differential - Rear Axle

1. Place the vehicle on a frame-contact hoist, allowing free rotation of the rear wheels.
2. Raise the hoist until the wheels clear the floor. Holding one wheel stationary, slowly rotate the other wheel approximately 1/2 revolution per second in both the forward and reverse directions. Wheel should rotate freely. If both wheels attempt to turn together, the differential is locking and is broken.
3. Raise hoist to maximum height with one person in the vehicle.
4. Start the engine, making sure that the engine is set at the proper low idle speed.
5. Apply the brake, then place the transmission in drive.
6. Have an assistant lock one rear wheel by pulling one parking brake cable from under the vehicle.
7. With the engine at low idle, slowly release the service brakes.
8. The locked rear wheel will remain stationary and the free wheel will begin turning. It is important that the service brakes be released slowly enough to start the free wheel turning and allow the free wheel to gradually increase in speed. As the speed of the free wheel is increased, the differential will lock, causing the rotating wheel to stop or both wheels to turn at the same speed. It may be necessary to accelerate the engine until approximately 16 km/h (10 mph) is indicated on the vehicle speedometer to cause the differential to lock. If indicated speed can be increased beyond 32 km/h (20 mph) without causing differential lock, the unit is not functioning properly. Rapid release of the brakes or clutch, or rapid acceleration of the engine will invalidate the test.
9. Lock the opposite rear wheel and repeat the procedure.