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Spec Smart: Don’t know your gear split chart from your rear axle ratio? Read our primer on medium-duty truck spec’ing

You run a handful of medium-duty trucks to get your product to market but trucking is far from being your first ord...

You run a handful of medium-duty trucks to get your product to market but trucking is far from being your first order of business. Speaking of business, it’s booming and your trucks are starting to show the wear that goes along with increased use. You know it’s time to replace them but you’re reluctant to start the process because your understanding of medium-duty truck spec’ing in minimal. Don’t sweat it. To help you make a more informed decision, we’ve prepared a quick primer to guide you through the spec’ing process.

The first thing to consider is your payload requirements. How much does each container that you haul weigh? How many of those containers do you need to get on a truck and what will be the resulting total weight? The vehicle you spec should reflect the maximum weight you need. Any more is waste, forcing you to spend more money than you need to for a higher horsepower engine. Heading to the dealer with the payload information under your cap makes for a much more accurate spec’ing process.

Work through a weight distribution chart with the dealer to ensure the truck can carry the desired payload and the weight distribution over each axle is within legal limits. Don’t forget to include the weight of devices such as refrigeration units.

Consider the places the truck will deliver to and check that its turning radius — the measurement from the centre of the rear axle to the front bumper — is sufficient. Cabovers are the better spec if the delivery points are particularly tight places or if weight in an issue. Don’t neglect to consider dock height. Increasing your payload by opting for a vehicle made lighter by spec’ing smaller wheels or lighter axles will cause problems if those options drop the height of the truck below what you need for the height of the loading docks it visits.

Consider where your trucks will do the majority of their hauling — whether it’s in the city, the highway or in suburban areas will determine how they should be geared. Trucks properly spec’d for city applications have higher axle ratios and lower speeds. Trucks spec’d for highway or suburban runs have a lower rear axle ratio for higher speeds and better fuel economy. Running city spec’ed trucks on the highway will eat away at your profit line through increased fuel consumption and piston crown and bearing failures in the engine.

There are two charts you will need to examine with the dealer to ensure the powertrain specs will do the job. A gradeability chart determines if the powertrain has the muscle to carry the payload over the type of terrain it will encounter. A gear split chart outlines how low on the rpm scale the engine can go to pick up the next gear. If your truck is improperly geared it will run in the higher rpm range to keep up with traffic, burning fuel savings in the process.

The skill level of your drivers will determine if you can get away with a basic manual transmission or if you need to upgrade to a synchronized manual or automatic that removes much of the shock new or inexperienced drivers place on the drivetrain. For most small private fleets, the person behind the wheel is not a professional driver but rather an employee such as a route salesperson or service technician using the truck to do his job.

Don’t get stuck on the sticker price. There’s more intelligent ways to help you make your final decision. Ask for an annual maintenance calculation, including A, B and C service intervals. Take a closer look at the standard components. Synthetic lube, for example, could be a standard spec for manual transmissions and rear axles. It will cost more but it can go 250,000 miles or more before it needs changing, saving about eight lube jobs and about $400 over a non-synthetic spec. Compare the warranties. Some warranties, for example, cover engine and axle casings but not internal parts.

Extra items such as air conditioning or an upgraded seat are worth the investment if they will measurably improve the productivity of your drivers. Some other options worth considering include heated mirrors, defrost systems that defrost the windshield and the side windows at the same time, tilt/telescoping steering wheels, power outlets for cell phones or lap tops, self-cleaning cab steps, service features positioned so that fluid levels are easily checked and extra insulation from engine and road noise.

In the end, even though trucking may not be your first order of business, the trucks you spec will play an important part in the cost of running your business. The greater effort you put towards making intelligent spec’ing decisions the greater the chance that they will pay off.

Truck News

Truck News

Truck News is Canada's leading trucking newspaper - news and information for trucking companies, owner/operators, truck drivers and logistics professionals working in the Canadian trucking industry.
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