2009 Hummer H3T Owner's Manual - Page 202

4-20 Driving Your Vehicle Log Crossing Using the proper technique, the vehicle will cross logs up to 10 inches (25.4 cm) in diameter. Approach the log at approximately a 15° angle (A) with the transmission in 1 (First) and the transfer case in Four-Wheel-Low Lock and "walk" the vehicle over, one tire at a time. It may be necessary to modulate the brake pedal and accelerator to avoid spin-out. Ease the vehicle down from the log with the brake. For very large dips, ditches or small washes, coast in, using the engine as a brake (transmission and transfer case lowest gears). Then, use the low ranges in the transmission and transfer case to power out. Roll The Tires Over Large Rocks Driving on Hills Off-road driving often takes you up, down, or across a hill. Driving safely on hills requires good judgment and an understanding of what the vehicle can and cannot do. There are some hills that simply cannot be driven, no matter how well built the vehicle. { CAUTION Many hills are simply too steep for any vehicle. If you drive up them, you will stall. If you drive down them, you cannot control your speed. If you drive across them, you will roll over. You could be seriously injured or killed. If you have any doubt about the steepness, do not drive the hill. Do not straddle large rocks; drive over them, letting the tire cover the rock. The tread of the tire is thicker and tougher than the sidewall of the tire and is more resilient to impact than underbody components.