Written by James Langan Friday, 18 December 2009 12:55
|Steve Johns 6.2L Diesel Hummer H1|
|Central Tire Inflation System|
Steve Johns loves his 1993 AM General HMC4 (4-door hardtop), powered by the stock 6.2L naturally-aspirated diesel. After years admiring the AM General H1, five years ago Steve purchased this clean specimen from his local GMC dealer for $25,000.00. It had only 50,000-miles on the odometer.
Ninety-three was only the second model year for the civilian Hummers – basically modified military trucks. (You can see the tan military paint showing through on Steve’s Hummer where the factory white paint has peeled away.) This H1 includes a 12,000-pound. Warn winch, undercarriage protection, air-conditioning, rocker-panel protection, a brush guard, tow hitch, and the Central Tire Inflation System (CTIS). This truck has every factory option offered in 1993 except power windows and door locks.
The bone stock GM V8 6.2L diesel is rated for 250 pound-feet of torque @ 2,000 RPM and 150 HP @ 3,600 RPM. Steve says in normal city driving the engine’s torque is adequate, but freeway on-ramps, passing and hills are difficult. By today’s standards, this old ‘93 is downright gutless, and Steve would like to wake-up the engine with a turbo or supercharger. Even without forced induction, Steve loves his old school 6.2L Hummer and has had zero problems with the engine while driving it to its present 76,000 miles. Steve has driven both the 6.5L turbo and 6.6L Duramax Hummers and was impressed with both. “Vastly improved,” is his take on the changes made to the newer H1 trucks. But Steve is keeping his trusty old 6.2L-powered Hummer: it’s paid for and set up the way he likes. Steve has considered an engine swap: buying a 6.5L engine would cost about $5,000.00 and a turn-key Duramax/Allison transmission conversion currently runs about $40,000.00!
Inside the H1, Steve has added a CB Radio, GPS, and an inclinometer to measure the sometimes-steep inclines he encounters. Outside, there is a Predator Motorsports roof rack, a spare-tire carrier and a rare GT products shell for the pickup bed. About 200 of these tops were built for the pickup and soft-top H1 trucks. They were built by a few manufacturers to GT’s specifications. Steve’s was made by Snug Top and sold exclusively through Hummer dealers for $3,000-5,000.00 when new.
Tires and Wheels
Light-truck tires are expensive and seem to be going up incrementally all the time. It’s common for enthusiasts to pay $250.00-$350.00 each for specialty light-truck tires, and rubber for an H1 is no exception. New Interco Swamper SSR tires in the H1 37x12.50R16.5 size are $320.00 each from mail order houses, and shipping usually isn’t free. When Steve needed two new tires he saved a bunch of money by choosing a pair of TreadWright, Inc. D-Mud retreads with Garnet Grip traction additive for the rear axle. The remanufactured TreadWrights were less than $150.00 each! The front axles rides on the standard 37x12.50R16.5 Goodyear MT tires. These tires are wrapped around factory aluminum wheels from a 2000 H1. All four tires are supported by rubber run-flats and the CTIS. The big tires and wheels on AM General H1 trucks can be difficult to balance, but Steve recently purchased a set of Centramatic continuous wheel balancers and says his H1 has never ridden so smoothly. All four tires continuously feel perfectly balanced.
Central Tire Inflation System
Adjusting tire pressures for off-highway traction (usually much lower than street PSI) is a common and very effective driving technique. Having the perfect air pressure for the conditions and putting as much rubber on the road as possible are primary elements of traction. The biggest negative to airing-down for off-highway travel is the need to air-up before driving at speed on pavement. Most off-roaders solve this problem with one of the many 12-volt compressors sold for this purpose, using either a portable unit or one permanently mounted to the truck. But the airing-up process can take a half hour or more depending on the tires and the compressor. For many enthusiast-level compressors, filling a tire like the H1’s 37-incher will cause them to overheat and quit before all four tires are filled.
The optional Central Tire Inflation System (CTIS) solves these problems and a few more. Instead of exiting the truck and slowly bleeding air from the valve stems, the CTIS allows the driver to deflate or inflate the tires on-the-fly. The CTIS includes an inflate/deflate switch as well as a rotary selector to choose either the front or rear tires only, or all four. Having the ability to fine tune the tire pressures from the cab is a great feature. As someone who often adjusts his tire pressures both on and off-highway depending on the load, I would love to have this option on all of my trucks.
The compressor is mounted under the hood, and has a coupler allowing the attachment of an air hose to fill trail companions’ tires or any other compressed air need. Steve has even used his on-board compressor to fill bicycle tires and inflatables when visiting nearby lakes. Some have reported problems with the CTIS. Steve’s system was serviced by his dealer before he purchased the Hummer and he’s never had a problem with it.
(Click any image for more information or to enlarge.)
About two weeks after purchasing the Hummer, still sporting temporary dealer plates, Steve joined the Nor Cal Hummer Group’s Sierra Snow run in the nearby Sierra Nevada mountains. After a few hours of easy snow driving, Steve failed to make it up a slight grade because he didn’t know how to use the brake-throttle-modulation technique to get the Torsen axles to hook-up. As the third H1 in a line of vehicles Steve quickly found himself stuck and blocking the trail. He had never owned a truck with a winch before and had no idea how to use one properly. Under the tutelage of more experienced members, he used his winch for the first time and easily extracted himself with a 30-foot pull. A few hours later, Steve again used his winch to pull out the ’00 H1 Hummer Wagon in front of him that had slid off the road and was stuck in a few feet of deep snow.
Steve’s slightly embarrassing worst stuck story involves a little mud puddle and his son Trent. Spotting a mud puddle in a construction area very close to their home, Trent said, “Daddy let’s go play in the mud puddle.” Steve obliged and drove off the road into the puddle. The puddle wasn’t enough for Steve and he ventured out into the field of mud for a little more play. After a short frolic, Steve turned around and headed back to the road. He started losing momentum and speed and soon found himself at a stop and very stuck. The clay-like mud was caked in the tires and packed under the truck; it even covered the bottom of the doors. Steve called a friend with a modified Chevy Blazer to pull him out. While waiting, Trent and Steve were offered help from a passing stranger driving a lifted, late-80s short-box Chevy pickup. Using Steve’s chain the little half-ton was not able to recover the beached H1. When Steve’s friend arrived he was impressed saying, “Steve, you’ve done it right my friend.” The full-sized Blazer tried but was also unable to pull the Hummer from the mud’s grasp. Both of these Chevys were heavily modified, sporting strong engines and mud tires, but they proved to be no match for the mud. With nightfall coming and headlights already on, the H1 was finally recovered after chaining the Chevy pickup and Blazer together, providing a sufficient anchor for Steve’s 12,000-pound winch to pull the Hummer free. It took Steve several hours, over two days, to remove all the mud glued to the General.
(Click any image for more information or to enlarge.)
Novice Test Drive
While on the trail ride for this photo shoot, Steve offered me the driver’s seat on one moderate hill climb. I have lots of saddle time in full-sized trucks, but looking out over the wide AM General H1 hood was a new experience. Getting the torque biasing Torsen differentials to hook-up using the brake-throttle-modulation technique proved challenging. I’m accustomed to traditional limited-slips, full lockers, and electronic traction control. I was either spinning tires or not moving forward. I then watched Steve drive up the same obstacle without spinning a tire. Apparently, he has mastered the technique!
Not Giving Up on the 6.2L
Steve regularly travels from his home in Reno, Nevada for Northern California Hummer events and to play with his Cool, California High Mobility 4x4 friends. Several times a year, Steve ventures into the deserts of Nevada, a perfect playground for the wide H1. At one time, he considered selling his Hummer, but couldn’t bring himself to part with the beast. He enjoys it too much. Despite the engine’s shortcomings, the H1 and the 6.2L diesel are a strong marriage and continue to work well. Steve and Trent are looking forward to racking up thousands of miles over the coming decades.
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