H2'S PREMIUM POWERTRAIN ANCHORED BY VORTEC POWER AND SOPHISTICATED FOUR-WHEEL DRIVE The HUMMER H2 combines class-leading Vortec power with a durable four-speed automatic transmission and a sophisticated four-wheel-drive system to stake its claim to being a true go-anywhere vehicle. "H2 provides excellent on-pavement power, performance and control for everyday driving and routine tasks like trailer towing," said Ken Lindensmith, H2 assistant vehicle line executive. "But its true character really shines in the off-road arena. It can easily soldier over rocks and through the harshest terrain." H2 can safely charge into six inches of water at 40 mph, for example, or travel through streams more than 20 inches deep at a leisurely 5-mph pace. It can also comfortably and confidently climb 16-inch steps and rocks, without getting hung up or jarring its passengers. And it can paddle through deep sand or run over sandy surfaces in high-speed desert conditions with remarkable ease. It's powered by a standard GM Vortec 6000 6.0-liter V8 producing 325 horsepower at 5200 rpm and 385 lb.-ft. of torque at 3600 rpm. The engine is mated to a heavy-duty 4L65-E four-speed automatic transmission, capable of out-muscling and out-torquing H2's premium off-road competitors. The H2's powertrain, aided by the 4L65-E's deep 3.06 first gear ratio, provides smooth launches and respectable off-line acceleration for a vehicle of its size and strength. The engine uses a new Hitachi throttle body as part of its precise electronic throttle control (ETC) system. ETC, a drive-by-wire system, provides a highly sophisticated and comprehensive way of controlling throttle position. In addition to information from the accelerator pedal, H2's ETC system also considers other available information, such as transmission shift schedules and whether the vehicle's transfer case is in "4 HI" or "4 LO" operating mode, to determine the optimum throttle progression for different operating requirements. The sophisticated four-wheel-drive system and transfer case are versatile and driver-selectable. The integrated Borg-Warner two-speed electrically controlled full-time 4WD system is capable of further reducing the vehicle's gear ratios by 2.64:1 when necessary, for highly controlled obstacle climbing. It provides a 40/60 percent front-to-rear torque split in "High Open" mode or when the differentials are unlocked and a 50/50 percent front-to-rear power split when the transfer case differential is locked. A specially designed low-range throttle progression allows the driver to precisely control engine speed (and as a result, the vehicle) during very rough terrain driving, and is automatically engaged when the transfer case is in "4 LO." The transfer case controls provide five mode selections, four of which can be accessed by dash-mounted button selectors. The fifth mode, neutral, is available by simultaneously pressing two of the button selectors. Selections include: 1) A high-range open or "4 HI Open" for normal, everyday driving on dry road surfaces at any speeds. 2) A high-range lock or "4 HI Locked" for semi-slippery surfaces like snow, light sand or wet areas, such as those around a boat launch; this selection locks the front and rear output shafts together, so their wheels rotate at exactly the same speed. 3) A low-range lock or "4 LO Locked" for severe off-pavement use, such as crawling over large rocks or logs. In addition to locking the two propshafts together, it provides a 2.64:1 gear reduction in the planetary gearset. By lowering the ratios of each of the gears, it adds the equivalent of another, extremely deep-ratio first gear and provides a great deal more torque for slow-speed climbing. Low Lock also activates a new, more measured throttle progression curve, which greatly enhances off-road driving comfort and control. High and Low Lock also allow a driver to select a different set of calibrations for the traction control system, using a separate "TC2" button. This provides additional wheel slip for select operating conditions and road surfaces, such as paddling through deep sand. 4) An Eaton electronic rear differential lock or "4 LO Locked + Rear Diff Locked," available only when the transfer case is in Low Lock position. It permits locking up the rear differential for optimum slow-speed capability in climbing over large rocks or up long, steep grades. It locks the two rear axle shafts together so they rotate at exactly the same speed-and does so electronically. (Since this mode can only be accessed when the transfer case is in Low Lock, the front and rear propshafts are already locked.) 5) "Neutral," obtained by simultaneously pressing the "4 LO Locked" and "4 HI Open" buttons and holding them down for 10 seconds. It permits flat-towing the H2 behind another vehicle. The H2 provides two different throttle progressions, depending on whether it is operating on pavement or off. With the transfer case either in a High Open or High Lock mode, the driver gets normal acceleration for everyday city and highway requirements. The "tow-haul" mode switch is available in either of these driving modes. This allows for a different shift progression of the transmission more suitable to trailering operation. However, off-road operation requires a slower, more controlled throttle response. Large-rock and obstacle crawling, in particular, demand both high torque and a very slow, carefully controlled vehicle speed, with no sudden movement. When the driver shifts into Low Lock, the H2's low-range throttle progression provides required responsiveness and control. With the new throttle progression curve (calibrated into the electronic engine controller) that it creates, a driver can step on the accelerator without opening up the throttle plate as quickly or fully. At maximum throttle depression, for example, the throttle plate only opens up to about 75 percent of its normal capability. And it takes longer, more throttle travel, to get to that 75 percent maximum, so power or torque are delivered in a more measured and controlled manner. Adding to the overall sense of control is a highly developed Bosch four-channel antilock braking/traction control system (ABS/TCS). In addition to providing optimum control on slippery surfaces, the ABS can detect and adjust its braking capabilities to rough off-road surfaces like gravel and potholes. The TCS also provides the ability to gain traction through a single wheel, if necessary. A second mode of the TCS system, "TC2," used in conjunction with the transfer case's selections, provides three additional operating modes: "4 HI Locked + TC2," "4 LO Locked + TC2" and "4 LO Locked + Rear Diff Locked + TC2." This provides distinct advantages in different driving conditions, such as loose sand or gravel in the desert or mud or slippery conditions. The H2's ABS is uniquely designed to detect rough-road surfaces and respond accordingly in addition to providing normal on-road control on slick surfaces. The ABS has separate control logic schemes to discern and react to deformable surfaces and provide the best solution for braking. As a result, the driver is frequently not aware that the ABS system is engaged, just feeling the sensation of a smooth responsive stop. In a very loose gravel surface, the driver may recognize added pedal travel during the stop, when the system has determined that more braking force is the correct solution. The result is an approximate 50 percent increase in deceleration on this surface condition. The Single Wheel traction control system provides additional capability under certain operating conditions. The system detects a slipping wheel and applies brake pressure to it to slow it down, transferring torque across the differential to provide traction for the wheel on the opposite side. The system senses any slipping wheels and applies the brakes to them individually, while the driveline and differentials transfer torque to the wheel with the high traction for added traction. A driver could have as many as three wheels on a slippery surface with virtually no traction and still get enough torque out of the fourth wheel to propel the truck up a 10 percent grade. Whenever the transfer case is in any locked mode, such as High Lock, Low Lock or Low Lock and Rear Differential Lock, a second selection, called "TC2," is available. The "TC2" button, as indicated, is on the dash in a separate block of controls just below the transfer case selections. TC2 frees the TCS up to provide more wheel slip on loose or deformable road surfaces like sand, where a driver typically needs to "paddle" through. Here, the vehicle might be going 10 mph, for example, while the wheels are spinning at 20 mph. With three transfer case selections, two rear axle differential selections and two modes provided by the TCS mode switch, the driver actually has total of seven driving mode selections, providing unprecedented versatility to tailor H2 performance to match driving conditions.