2010 Hummer H3 Owner's Manual - Page 239

Driving and Operating To lock the rear axle, do the following: 1. Place the transfer case in the 4LO Lock mode. This is the only mode which will allow the rear axle to lock. See Four-Wheel Drive on page 9‑46 for more information regarding the transfer case and 4LO Lock mode. 2. Press the rear axle locking button with the vehicle moving less than 26 km/h (16 mph). The light in the button stops flashing and remains illuminated when the rear axle is locked. Notice: If you try to lock the axle while the vehicle is stuck and the tires are spinning, the vehicle's drivetrain could be damaged. The repairs would not be covered by the vehicle warranty. Always lock the axle before attempting situations and/or navigating terrain which could possibly cause the vehicle to become stuck. The locking rear axle will be disengaged when the wheel speed is greater than 64 km/h (40 mph), if the vehicle's battery is low and/or the transfer case is shifted out of 4LO Lock mode. Notice: If the vehicle's axle is locked while driving on pavement, the drivetrain could be damaged. Repairs would not be covered by the vehicle warranty. Do not use the locking axle on pavement. If four-wheel drive is needed when traveling on pavement, use only 4HI. 9-55 Locking Front Axle For vehicles with this feature, the locking front axle, used with the locking rear axle, can give the vehicle additional traction when traveling in off-road situations such as mud, snow, sand, steep hills and uneven terrain. The button used to turn the locking front axle on or off is located on the instrument panel. Before the front axle can be locked, the rear axle must be locked.