By Bruce W. Smith The exploding CV-joint on the right front axle of the H3 Hummer pickup ahead of us sounds like a rifle shot as it reverberates off the California Sierra’s rocky terrain and tall timber overshadowing the Swamp Lake OHV trail we are driving along. “Sounds like the mule just broke a leg,” my seatmate says with a wry grin and a touch of an engineer’s dry humor. A little too much throttle, rear tires off the ground wedged between a boulder and a log, and a fully extended front suspension brought about the sudden catastrophic parts failure under the front of the white Hummer H3 “T” that now blocks our only path back to civilization. But it’s not unexpected or a matter of concern. In fact, such parts failures are exactly what the Hummer engineers we are off-roading with want to see. “This is why we take our ‘development mules’ on these off-road drives. We push them hard and when something breaks or malfunctions, it’s just part of our overall development process to ensure they are more than ready to handle what their future owners dish out,” says Gary Williams, H3/H3T Program Engineering Manager and one of six Hummer engineers on this two-day adventure over the rugged 13-mile-long Swamp Lake OHV Trail near the town of Shaver Lake, California. “We’ll do a thorough inspection of the broken CV joint and analyze the
situation in which it occurred when we HIDDEN GEMS The H3T “development mules” Williams refers to is the pair of heavily camouflaged white Hummer H3 pickups—one a 5.3L V8 model with an automatic, the other a 3.5L I-5 manual. Both have black bras over the front ends and matching covers that extend from the top of the four-door cab back to the rear and down to the lower body panels, completely covering the back half of the truck. But we know what lies beneath the rear camo: It’s a real pickup bed. Code-named “GMT 745” by GM, the new four-door pickup is based on the existing H3, but with the chassis lengthened 23 inches to accommodate a five-foot Colorado/Canyon bed and a full-size rear doors. When we’d met up with Williams and the Hummer H3 pickup engineering development team in Fresno, some 50 miles to the west of where we now stood watching the repairs get underway, we were told the bed is designed for full functionality. It will come with the same tie-down system and bed liner style as found in the new full-size GM pickups, and for those who like to carry ATVs and other loads, the bed measures 48-inches between the wheelwells. It also has top-access bed-rail storage bins on each side for added cargo storage and a bed-extender to accommodate longer cargo needs.
As Daryl Ehrlich, the H3/H3T powertrain development engineer, muscles a race-style Craftsman floor jack between the broken-down mule and the boulders underneath, John Chapman, the head wrench who is also a technician at GM’s Desert Proving Grounds in Arizona, pulls out an electric impact wrench. I look at my watch. Less than 20 minutes have gone by since the CV-joint disintegrated. Now the tire is back on the hub, Chapman is wiping axle grease form his hands, and we’re ready to get moving again. H3T LIFE CYCLE Dominic Rimmer, the H3T Vehicle Performance Integration Manager who does his own choreography between production and engineering in Brazil where the H3s are built for sales outside of North America, slides into the seat next to me. As we slowly make our way along the remaining mile or so of trail, he
explains the basic evolution of the H3T.
The first phase is the idea is brought to life both virtually (using powerful computer-aided drawing programs) and physically as a one-off, “Proof of Concept” vehicle hand-built by their team in GM’s Experimental Engineering facility at GM’s Milford Proving Grounds. The resulting 134-inch-wheelbase concept pickup looked good despite welded-on door extensions and mix-and-match of parts from other vehicles. But sophisticated computer simulations and early development drives of the hand-built “Proof of Concept” truck revealed the longer wheelbase H3T needed a number of upgrades and changes to ensure it met and exceeded the expectations of future owners. Rimmer says after those initial changes were made and they had a definite direction for the truck they hand-built some two dozen “mules” in Warren, Michigan, to use as rolling design and engineering test platforms. These mules are put through a seemingly unending series of tests at GM proving grounds around the country—and in real-world driving conditions from Death Valley to, well, the Swamp Lake Trail we are now driving.
FINE-TUNING OVER TIME Over beers, baked potatoes, and fresh trout at our overnight camp along the edge of Shaver Lake, Todd Hubbard, who oversees the H3/H3T ride and handling, says an extraordinary amount of seat time was devoted to making the new Hummer pickup handle well both on- and off-road. Hubbard says they spent hundreds of hours tuning the suspension so the pickup’s 55/45 front/rear weight distribution was well-managed both on-road and off, paved or gravel, towing or unburdened. What remains in the H3T’s development cycle is putting 45-50 “integration vehicles”—those actually built on a production line in Brazil—on the road where GM drivers will put more than 500,000 miles under their wheels. Many of these will be sacrificed in lab crash tests. The others will crushed or used as parts donors for the next generation Hummer. The final build before actual production begins in mid-2008 will be another 100 or so pre-production H3T models. Eventually these trucks, too, will be “recycled” or crushed. As I turn the switch on the console from “4L” to “2H” that thought saddens me. Two days behind the wheel of this new Hummer pickup has shown me just how good a vehicle this is for those who want that Hummer look without sacrificing anything in utility value and performance. I make one last attempt at saving one of these mules from a pre-destined fate. “Honest, I’ll keep it in a car hauler trailer and only use it off-road,” I mock a hands-clasped plea to Williams as I exit the V8-powered white H3T. He smiles. “Nice try.”
Daryl Ehrlich, the H3/H3T powertrain development engineer, downloads massive amounts of data from the H3T’s onboard computer during a stop on the drive. Captured data is then distributed among the engineers back in Michigan where they pour over every minute operating detail of the H3T’s drivetrain and cooling system. They can then make programming changes as needed in the development process.
The back “Proof of Concept” H3T (right) was hand-built to give engineers a rolling platform from which to work. The white “mules” came later and were built on a production line. The mules reflect about 90-percet of what the actual production 2009 H3T will be like when it arrives in mid- to late 2008.
The optional “Adventure Package” to be offered in the H3 pickup will include these 33-inch Bridgestone Dueler A/Ts and special alloy wheels.
You’ll never see this Hummer pickup in production. It’s a Regular Cab shortbed Colorado body sitting atop an H3 chassis. John Chapman and Dave Williams, the two mechanics/technicians from GM’s Desert proving Grounds in Arizona, that accompanied us, had it custom built as their chase truck.
A sneak look under the rear camouflage reveals the five-foot Colorado/Canyon pickup bed. The three H3Ts in our group were loaded down with provisions, spare parts, and camping gear stored in cargo boxes all secured utilizing the GM cargo tie-down system along the bed sides.
What is impressive about the Hummer H3 pickup is the excellent suspension tuning and long wheel travel. It is very sure-footed off-road.
The rock rails on our test vehicles got a hard workout along the 13-mile-long Swamp Lake Trail. Hummer engineers designed the rails—and skid plates—to hold the truck’s entire weight just like the bigger H2.
Bridgestone Duelers were dropped to 20psi for the trail. Tires worked remarkably well. Not a single flat on the trip despite constant encounters with rocks of all shapes and sizes.
Excellent suspension travel, front and rear locking diffs, and quick steering allowed the long wheelbased H3Ts to traverse terrain the typical owner would never think of driving.
Hummer program manager, Gary Williams (center left) shares early morning hot coffee and a few laughs with others in our two-day long development drive in the high Sierras.
If time is a factor in making unexpected trail repairs, there’s no one faster than Hummer’s John Crawford. This master mechanic replaced the broken CV-joint in one of the H3T mules in less than 20 minutes while working on the rocks.
Broken parts are to be expected when pushing prototype vehicles well beyond what would be considered typical driving situations. These parts will find their way to Hummer’s engineering center in Michigan for a detailed analysis of what failed and why. 2009 HUMMER H3T PRELIMINARY SPECIFICATIONS
Engine
Transmission
Chassis/Suspension
Brakes
Wheels/Tires
Dimensions
Interior
Cargo Box
Capacities
*Pending SAE certification. Note: Information shown is current at time of publication. |
PROVING
GROUND
get these trucks back to our development center in Warren [Michigan]. If
it’s determined there’s a problem with the parts, then we still have time
to address that issue before the H3T goes into actual production.”
The trucks
we are driving are equipped with the “Adventure Option Package.” This
option includes 33-inch Bridgestone Dueler A/Ts and an electric-locking
front differential—both of which prove their worth on this trail. 
Such a
development process is what has brought about the reinforced drop-frame on
the new H3T; larger diameter front and rear anti-sway bars; recalibrated
shock tuning; V8 steering pump on the 5-cylinder model; a quick-steering
rack & pinion for both the I-5 andV8 models; higher capacity cooling
system; and 32-inch tires on new 16-inch steel wheels with 33’s and the
electric locker as an option package.
