All terrain mediums

Canadian Forest Industries, Nov/Dec 2004 by Elmer, Howard J

The new Kodiak/TopKick line from Gm finally has what logging customers have been looking for: 4WD

Going into its third year of production, GM's medium duty truck sector had an obvious shortcoming: No 4WD option. This fact has left much of the off-road based business in the hands of competitor Ford. But a recent demonstration of new product at the Milford proving ground in Michigan shows that GM is back in the running.

"The GM-installed 4WD option is something commercial customers and dealers have been asking for," says Elliott Benson, product manager for the Kodiak C4500 and C5500 models. "These new models will meet the needs of buyers in forestry, snow plowing, landscaping, agriculture, utility work and more."

A key feature in GM's 4WD system is an electronically controlled New Venture Gear Model NV273 two-speed transfer case and an instrument panel-mounted rotary dial for activating 4L, 4H and 2H settings. Kodiak models also feature manually activated front locking hubs for additional traction and a heavy-duty off-road skid plate protecting the transfer case. The trucks also feature electronic throttle control that smoothes out low-speed manoeuvres, and larger, 15-inch brake discs front and rear.

First offered in 2003, the TopKick C4500-C5500 trucks offered regular and commercial cutaway chassis cabs and vocational packages to cover school bus, fire and rescue, ambulance, shuttle bus, wrecker and snowplow setups. GVWRs range from 16,000 lb to 19,500 lb. The 4500 series (16,000 GVWR) will also be available as a Chevy Kodiak model. The 4500 essentially replaces the old series Chevy 3500 HD pickup cab model. The model line has expanded to cover Class 6, 7 and 8 trucks as well. In 2004, a crew cab model was added, now available across the line.

Low cost conversions

GM says special attention has been paid to the cost of modifications for the upfitter. All models share a stamped, straight-section, C-channel frame that provides a clean back-of -cab design available in varied strengths of 50,000 to 80,000-psi steel. This year C6500 - C8500 models use an even heavier 120,000-psi heat-treated frame.

There should be no need to re-route or change any OEM component. Frame rails are flat, connected with web supports and are uninterrupted by bolt or rivet heads. Chassis and axle combinations are offered in 16 regular production wheelbases that will net GVWRs ranging from 16,000 to 61,000 lb and allow for the mounting of up to a 30-foot body on a single axle without having to add to the frame.

Drivability on these vehicles is much improved thanks to key design elements like: a set-back axle with a wheel cut of up to 54 degrees (35-foot turning circle on the shortest wheelbase); a larger windshield and a new sloped hood that offer better visibility (13.8 feet in front of the truck, measured from the bumper); new seating combinations; and a cleaner, better designed interior. In addition A-pillar mounted breakaway mirrors are standard, as is the re-designed steering system that complements the shorter axle turns. GM adds that none of the turning ability has been lost with the addition of the 4WD option.

Across the board, the general powertrain choices are either the 6600 or 7800 Duramax, the Cat 3126E diesel or the Vortec 8100 gasoline engine. Transmissions are either Allison automatics or Eaton Fuller manuals. The 6600 puts out 300 horsepower at 3,100 rpm, with 520 foot-pounds of torque at 1,800 rpm. The 8100 gas motor strikes 325 horsepower at 4,000 rpm and reaches optimum torque of 450 foot-pounds at 2,800 rpm.

Both the diesel and gas engines are mated to either a five-speed automatic Allison transmission or a fully synchronized ZF six-speed Class 4 and 5. Also a Power Take Off (PTO) option is available in these classes with the Allison.

For 2005, many of the Allison transmissions have been recalibrated and also offer longer warranties - up to 100,000 miles. Also Allison vocational transmissions have also been added to the C6500 and C7500 models. This 2500 HS Series transmission also has an increased GVWR of 33,000 lb, up from 30,000 lb in 2004. The Allison 3000 RDS close-ratio six-speed transmission is now the base transmission on C8500 models. It's also available on C6500 and C7500.

The inline six-cylinder diesel lineup features 11 ratings for the Caterpillar engine and a special version of the Duramax 7800. This engine offers a total of 10 separate power ratings and mates to Eaton Fuller and Spicer manual transmissions.

Interiors feature pickup-like instrumentation and steering wheel, driver's bucket seat (air-ride seat available), single or dual passenger seat that also incorporates storage, armrest and workstation. New this year is a two-person seat option. The seat comes in grey vinyl only and has a fixed seatback. To make room for the seat, the centre console and cupholder are removed. This option is available on all regular cab models.

Fast service access

New service design initiatives include a process called "Priority Access System." Engine components are grouped into modules with the engine compartment. Groups are then removed together or independently by a technician - in specific sequence - to gain access as required. Since the introduction of this system, J.D. Power and Associates has rated these mediumduty trucks with the least amount of unscheduled downtime in their class, GM says.