Factory Made 4x4s Go Almost Anywhere

Sept. 28, 2010


GM began building C4500 and C5500 4×4s at its Flint, Mich., plant in July. This Regular Cab version with a heavy "digger" body rode smoothly on streets and highways.
Steep grades (top photo) and a dirt trail strewn with telephone poles are among the obstacles on GM's off-road course at its Milford, Mich., proving grounds. Here (above) we see the correct way to step over a pole, but one driver got his truck hung up on the end of a pole.
Crew Cab versions use smart-looking, purpose-built rear doors. The high-profile chassis demands a healthy climb up, and a van-derived cab floor is several inches higher than door sills.
Interior parts, including steering wheel, transmission shifter and instrument panel, are lifted from GM's light trucks. Everything is easy to see and use.
A tight wheel cut makes for excellent maneuverability. Optional 4×4 gear includes a Dana 60 front-driving axle with manually locking wheel hubs.In this story:

This must be "the year of the four-wheel-drive medium-duty truck," as several builders announced the availability of factory-assembled 4×4s. These are mainly for use by landscapers, drillers, machinery servicers, public utilities, recreational-vehicle enthusiasts and others who take their trucks into rough terrain where extra traction is required.

One of those builders is General Motors, which in July began making its Class 4, 5 and 6 GMC TopKick and Chevrolet Kodiak models with optional four-wheel drive on its regular assembly line in Flint, Mich. Prior to that, GM filled orders for C4500 and C5500 4×4s by sending completed 2×4 chassis to Monroe Truck Equipment's nearby modification center.

Monroe did similar work when GM's mediums were built in Janesville, Wis., and still does some 4×4 upfitting in Flint for the heavier C6500, C7500 and C8500 models. Various suspension and axle capacities give the C4500 gross vehicle weight ratings from 16,000 to 17,500 pounds, and the C5500's GVW ratings are 18,000 to 26,000 pounds.

Factory assembly saves money for GM and its customers, said Mike Eaves, a product planning manager, because the truck's front end doesn't have to be taken apart for conversion. Everything goes in as ordered and nothing has to be removed later for a conversion. So factory building saves a customer 40 percent or more on the upcharge for the 4×4.

A C4500 or C5500 4×4 gets a New Venture Gear 2-speed transfer case, Dana front-driving axle and a Spicer driveshaft, plus a high-profile parabolic leaf-spring suspension to provide room for the extra equipment, plus electric controls to activate and deactivate it. All parts are warranted by GM and can be serviced at any GM commercial truck dealer.

About a month and a half after 4×4 assembly began, GM Fleet & Commercial, the corporate arm that designs and markets trucks like this, displayed them and a variety of other specialty vehicles outside Detroit. The day included time with pre-production 4×4s at GM's Milford proving grounds, plus mileage on public streets and highways with production versions.

Off-road driving impressions

Off-roading was instructive because we experienced some of what the 4×4s will go through. That ranged from steeply inclined trails to soft sand, but sadly, no mud. There also was a wide dirt track blocked by old telephone poles, which the trucks easily climbed over if driven correctly.

One reporter, however, let his truck's right-front wheel drop off the end of a pole and a tie-rod end hung up on the pole's edge, hanging the wheel so its tire barely touched the dirt. So that wheel spun uselessly as the open differential continued to send power its way, and the rear wheels lacked enough traction to push the truck off the obstacle. A gentle push from my truck was all that was needed to free the stuck one.

The driving lesson is to keep all wheels where they can grab the ground and keep working, and keep any part of the undercarriage away from humps where they can hang up. Equipment-wise, locking diffs would help, but they aren't available from the factory.

Typical of modern part-time four-wheel-drive systems, a rotary switch on the dash allows on-the-fly shifting between 2 Hi and 4 Hi. Before going into or out of 4 Lo, though, you have to stop and shift the transmission to Neutral. You also have to get out to lock or unlock the steer axle's manual hubs so the front wheels can get power or not.

There was plenty of power whether the V-8 engine underhood was the standard gasoline-burning, 496-cubic-inch Vortec 8100 or the optional 403-cubic-inch Duramax 6600 diesel. The Duramax makes 210 or 300 horsepower and the Vortec puts out 225 or 325 horsepower, and I used them to move briskly over the course's rough sections, causing my passengers to hang on amid spirited bouncing of the chassis. "Jeez, Berg!" some barked, but usually they were grinning. You can't beat fun.

On-road impressions

For on-road travel, we could choose from various C4500 and C5500 4×4s, and one of those I grabbed was the red C5500 Regular Cab with the heavy "driller" body you see on these pages. The truck rode well over all types of pavement, though the great majority of the routing was over smooth asphalt.

A wheel cut of up to 53 degrees means the truck is capable of tight turns and high maneuverability, which is helpful in any cramped situation. Making this possible is the front axle's setback position of 37 inches behind the bumper. This allows the steering gear to be mounted well forward and out of the way of the front wheel as it pivots toward the right. The power steering was precise if slightly vague, as you'd expect with the front-driving axle.

Though these are hefty trucks, the C4500/5500s' agility helps them feel smaller. They accelerate well with those gutsy engines, either of which comes with an Allison 1000 5-speed automatic transmission. No manual transmission is available now, though one might come later, marketers said.

The auto tranny's shifter is on the column, like in GM's pickups and vans. In fact, most interior parts, including a smallish steering wheel and about a quarter-acre of plastic panels, are from GM's G-series vans. All these things contribute to the small-truck sensation. The selector—as well as the gauges, switches and controls—are all easy to see and use.

Older GM midrange conventionals have pickup-based cabs. But the current C-Series, introduced in the summer of 2002 as '03 models, uses steel panels from G-Series vans. So the cabs, which Mike Eaves said are reinforced for medium-duty service, are wide and roomy, which is a plus for any truck whose driver is part of a two- or three-person crew.

The four-door Crew Cab version, introduced early last year, can be set up for as many as six people. Its rear doors are purpose-built for this application, with vertical leading edges that line up smartly with the trailing edges of the front doors. Ford does it this way for its SuperDuty models, which are GM's main competition.

A couple of other competitors use four front doors; the angled forward edges of those used as back doors look ungainly, and add extra length to their crew cabs. The GM Crew Cab has generous front and rear leg room and adds only 41 inches to the length of a two-door Regular cab. GM does not offer an Extended Cab in the C-Series, though several competitors do in their comparable models.

While the GM doors look appropriate, they close with a "thung" rather than a solid "thunk," and the hinges squeaked in a couple of in-service C-Series trucks I've driven. Keep your oilcan handy and hope that squeaks are the extent of any problems.

While seated, a driver and passenger peer through a big, sharply sloped windshield. Its base is well ahead of the dashboard's rear edge, so anyone trying to clean the lower portion of the glass has a long reach in store. Then again, the dash's top-facing surface forms a big shelf to put stuff on. Side windows are large and views forward and to the sides are good. Mirrors on unusual single-arm mounts provide good pictures to the rear.

The cab floor sits several inches higher than the doors' lower sills—another result of deriving the cab from the G-vans—and requires an extra short step up or down while getting in or out. A 4×4's higher stance demands a longer climb, which was awkward with the pre-production trucks, but pretty good due to well-placed steps and handles on production models.

So, jump aboard and experience these nimble and quick medium-duty models with their really roomy cabs. Opt for that 4×4 gear and you've got competent, comfortable, and competitively priced trucks that'll take you and your workers almost anywhere they need to go. See you in the dirt.