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A Midsummer Day’s Dream

Picture driving through the scenic back roads of the Kawarthas on a sunny midsummer day as part of a GMC truck convoy whose sole purpose, aside from putting the new Kodiak and TopKick Class of 4-8 mod...


Picture driving through the scenic back roads of the Kawarthas on a sunny midsummer day as part of a GMC truck convoy whose sole purpose, aside from putting the new Kodiak and TopKick Class of 4-8 models to the test, of course, is to deliver stone to a local Boy Scout Camp in need of some help with an outdoor project.

That’s the invitation Phil Kling, Manager of Product Communications at General Motors of Canada, dangled in front of me earlier this summer. What he didn’t know at the time was that aside from offering me a welcomed day out of the office, he was providing me with a chance at a “back to the future” type of experience. You see, I have a particular interest in the TopKick product. The initial launch of the line back in the late 80s was the first press conference I attended as a trucking scribe; the tour of the Janesville, Wisconsin plant where the truck’s initial production was handled served as my first view of the internal workings of a truck plant; and the test drive of the TopKick a while later marked my initial experience behind the wheel of a heavy truck.

So, plainly, there was no denying Kling’s invitation for a test drive.

The new Class 4-8 models were first previewed for Canadian truck buyers at last year’s Truxpo and Expocam shows and introduced to the market during the first half of this year as 2003 model entries.

The C4500/C5500 Series (Class 4-5) includes regular, crew cab, and commercial cutaway chassis cabs. Two-wheel-drive models options are particularly strong in this segment: GM’s engineers have come up with eight two-wheel-drive models, which is five more than what was previously available. The C4500/C5500 Series offers six niche vocation packages including ambulance, fire and rescue, school bus, shuttle bus, snowplow and wrecker applications. The C4500 has a 16,000-pound GVWR while the beefier C5500 is available in 18,000 to 19,500-pound GVWRs.

Looking at the heavy-weight lineup, the GMC TopKick C6500, C7500 and C8500 (Class 6-8) Series trucks replace GM’s C-Series conventional cabs. Initially they are available in two-wheel-drive regular cab, commercial cutaway chassis and crew cab. With a GVWR ranging from 19,501 all the way up to 61,000 lb and models which include low profile, tandem and tractor variants, GM has positioned this series to compete in the low-end of the Class 8 heavy-duty market.

Judging by the general specs provided it seemed GM’s design engineers had gone out of their way to produce a new line that offered truck buyers a healthy variety of options. But how did those trucks look and handle in the field?

The new truck convoy was prepped up and waiting for our circle check inspection at the company’s Oshawa, Ontario, corporate offices. Although the look of the Kodiak and TopKick line still bears a fair resemblance to the trucks I drove more than a decade ago, GM has done a considerable amount of redesign and reengineering work. What immediately hits the eye standing outside the truck and even more so soon as you sit behind the wheel is the sloping hood. The C4500/C5500 models, which were the first of five trucks I drove that day, have been designed with such great visibility that you can see ground objects as close as 13.8 feet in front of the truck from the front bumper. That, GMC points out, is better than the forward visibility of many compact pickup trucks and comes in handy in busy work sites. Their heavier truck cousins, the C6500/C7500/C8500 models, are built with higher frames and cabs but still manage to provide 18.8-foot forward visibility. The windshield is appreciably larger too – 25% larger, in fact, than in previous models. And, particularly helpful for infrequent truck drivers such as myself, are the larger, convex outside mirrors for rearward visibility.

The cab is also roomier and more comfortable than what I remembered from the previous design. The regular cab offers seating for one, two or three passengers and the crew cab offers seating for up to six passengers. With the crew cab spec the front passenger seat and rear seats can be deleted to create additional interior room. The instrument panel is very easy to read. Its centre curves out and angles towards the driver, which provides a direct view of the controls and gauges with just a slight turn of the head. The instrument panel also includes up to 24 telltale warning lights and gauges.

We got on to the highway and into some of the rolling back roads characteristic of this part of the country pretty quickly on our test drive and I was immediately impressed with the display of muscle shown by even the Class 4 and 5 models in climbing some fairly steep hills. The C4500/5500 models are powered by the newly available Duramax 6600 turbo V8 diesel, which is available with 300 hp @ 3100 rpm and 520 lb-ft of torque at 1800 rpm. There is also a lower-rated version designed for improved fuel efficiency and producing 210 hp @ 2750 rpm and 520 lb-ft of torque @ 1800 rpm. For truck owners where fuel efficiency is not an issue due to low daily mileage, the gas engine with its considerable upfront savings may make sense. GM’s standard Vortec 8100 gasoline engine is now available with a V8 rating of 325 hp @ 4000 rpm and 450 lb-ft @ 2800 rpm. A lower-rated version, with 225 hp @ 3600 rpm and 355 lb-ft of torque @ 2400 rpm is another possible spec. The Vortec engine can also be converted to alternative fuel use. The C6500/C7500/C8500 models can be spec’d with Duramax 7800 six-cylinder diesel or the Caterpillar 3126E.

Both the Duramax 6600 and Vortec 8100 mate to a standard, fully-synchronized ZF S6-650 six speed manual transmission or optional electronically controlled Allison five-speed automatics. Truck transmission technology has come a long way over the past decade and that was evident on the test drive. The easy shifting provided with the six-speed manual provided probably the best impression of the day. It was basically little different that driving a manual on a car with none of the gear fighting I recalled from earlier offerings. The Allison automatic option, meanwhile, provides Power Take Off for the first time in a conventional cab GM Class 4-5 truck. Allison 2000 Series transmissions are standard with the C6500/C7500 with an Allison 2400 as an option. The C8500 single and tandem models have Allison’s MD 3000 Series as the standard spec.

Although the engine options had the muscle to easily climb even some of larger hills we tackled, they were still quiet enough to allow for casual conversation without the need to raise your voice. GM says it has managed an impressive 50% reduction in noise, vibration and harshness and the results were clearly evident over the 7-hour test drive.

While we didn’t have a lot of opportunity to really put the trucks’ maneuverability to the test, the few opportunities we had in trying to maneuver around a sand and gravel pit and the parking lot of the country club where we stopped for lunch (nothing wrong with mixing pleasure with business, and the parking lot was under construction and so required some adept maneuvering) did provide an indication of what these trucks can do. GM has improved maneuverability with the new models by employing a new steering geometry which includes high inside turn angles, longer front suspension springs and a slightly set-back front axle. As a result, a regular cab C5500 with an 84-inch CA will out-turn (curb-to-curb diameter) a comparable Ford product by almost 19 feet, GM claims. Almost all of the models also use wide 80- to 82-inch front tracks, which permit wheel cuts up to 53 degrees.

Funny thing about the ride: About five hours into the test drive I noticed that I hadn’t jotted a thing about the ride – rather peculiar for such an important driver-related issue. When I thought about it I realized it was because the ride had been so smooth it had almost become a non-issue. True we didn’t spend our time in gravel pits but back roads in Ontario are not the best maintained. Hystec cab mounts on all models isolate the cab in all directions and dampen the ride. The Hystec mounts attach at the front and are filled wi
th stacked-up plastic discs, sitting in lubrication, which allows GM engineers to “tune” the damping. The C6500/C7500/C8500 models have a three-point cab mounting system, which employs a “bridge support” at the rear for extra isolation. It uses a very large body mounting bracket, almost like a crossmember, with “legs” that attach to brackets on the front. At the centre of the “bridge”, a cushion sandwiches each bracket. The C4500/C5500 models have a tapered leaf and multi-leaf spring suspension. A new four-point cab mounting system is also specially designed to handle the flexing capability designed into the new frames.

Finally, a note about those frames. Hauling in and out of sand and gravel pits there’s plenty of situations where a truck can hit a ditch and twitch a frame. GM’s engineers said that they kept than in mind when they demanded that with the new design even the lowest-rated frames had to have a higher strength rating than the 36,000 psi rating of the steel used in some competitive frames.

General Motors has sought to redefine the limits of medium-duty truck capability with its new generation of Kodiak and TopKick models. After a whole day spent driving their impressive new truck lineup, I think it’s fair to say it warrants close consideration for vocational businesses looking to upgrade their truck fleet.


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