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    Credit: Kenworth Truck Co.


Some key questions that need to be answered concern the loads that you expect to haul. For example, you will need a different chassis spec when hauling bulk loads such as asphalt, sand or gravel than you would if you hauled mostly demolition debris.

If you're planning on visiting a lot of demolition sites or are hauling heavy rock, you will need to have the body and suspension beefed up to handle the pounding it will take from the large masses going in the dump body. Your body supplier will have input on this.

The hauling question relates to the environment or roads you are operating in. Are you going to spend a lot of time on very rough jobsites or will most of the hauling be long distances on smooth gravel and sealed roads?

"If you will be going off-road a lot into rough terrain, you'll need a suspension that is heavier duty and has more articulation," Kenworth's Parlier advises. "But if you're hauling longer distances, you'll need to consider the trade-off between the ease of dumping and the ability to haul more load per trip. For example, a transfer dump will allow you to haul more with one driver, but it will take longer to unload. Double bottom-trailers carry a lot of payload, too, but with those you're limited on where you can drop the load - it's a lot harder to dump gravel into a hole for a swimming pool, for instance, with bottom dumps."


One of the big mistakes many people make with dump truck engines is they spec too much power, says Parlier. "You should get just enough horsepower to do the job. Generally, 350 to 400 hp is plenty for most applications. Extra horsepower just uses more fuel, puts more strain on the rest of the drivetrain, and adds cost up front.

"If you go with a smaller 13-liter block, you save around 700 pounds over a 15-liter block," Parlier says.

The transmission installed with the engine needs a lot of ratio range. You need a low enough gear to get out of a hilly jobsite and high enough top gear to attain decent highway speeds. The Eaton Fuller 8LL transmission is a common truck spec, but she suggested an 18-speed transmission for larger and heavier trucks. "The 8LL gives you two low gears for startability off-road and enough top-end range for the highway," says Kenworth's Parlier. "But if you are hauling over 90,000 pounds, you should consider an 18-speed because you get much closer splits from bottom to top."

The typical dump truck uses rear axles rated at 46,000 pounds. This covers most trucks, from 14/16-yard solo dumps through combinations up to 110,000 GCW.

Another thing to remember for operating off-road is air filtration. Lots of drivers love the look of dual polished external air cleaners, and these provide excellent filtration with low air restriction. But they are quite expensive compared with under-hood air cleaners. A little money spent up front on a better air cleaner is cheap compared to a dusted engine. And better filtration will usually mean longer life for the filter elements. For example, dual 15-inch air cleaners will last over 7 times as long as a single 11-inch underhood air cleaner before needing replacement.


If you are hauling a lot of loads per day, cutting vehicle weight can be profitable. You can slim down by spec'ing components - such as wheels, air tanks and clutch housings - in aluminum rather than steel. "Use the smallest fuel tank you can get away with," Parlier adds. "Some operators can get away with a 56-gallon tank, but most will need at least 75 to 90 gallons to get through a day."

You can also save valuable pounds by choosing the right suspension. "The difference can be as high as 400 pounds," Parlier says of the different suspension options.

To avoid hauling around extra steel in the vehicle frame, have the dealer work with a Kenworth application engineer so that you only get enough frame where you need it. You will typically need a strong crossmember at the back of the cab to strengthen the hoist mounting area. If you are planning to add lift axles later, make sure the dealer adds that information to the order so that the frame can be prepared for them.

But remember that many of these weight savers will cost more up front. You will need to balance that against the gains you expect to make hauling more payload.


Finally, consider a few driver performance-related items. To get the best turn performance and road feel from steering, Parlier recommends dual small gears rather than a large single steering gear. The dual system will also last longer than a single system.

Try to spec as much glass area as possible. "Kenworth DayLite(R) doors give a larger glass area in the main door window," Parlier says. "You also want plenty of mirrors."

On a topic related to windows, Parlier suggests picking low-replacement cost windshields when they're available. "Most vocational fleets replace at least one windshield side per truck per year. Two-piece flat-glass windshields with roped-in seals can be replaced in half an hour for a total cost of under a hundred dollars. This can save thousands of dollars over the life of the truck."

With lift axles, it's smart to get a six-channel ABS system. "Lift axles, especially steerable ones, are normally over-braked for the load," Parlier says. "By including them in the ABS system, they're less likely to lock up and you reduce tire flat spotting."

To enhance truck productivity and the driving experience, consider adding a navigation system like the Kenworth NavPlus(R), Parlier says. It offers true truck navigation by Garmin, communication, diagnostics, and infotainment technologies. The system, developed on the award-winning Microsoft Windows Embedded Automotive software platform, is fully compatible with the Kenworth Electronic Service Analyst (ESA), a computer-base diagnostics tool, which simplifies troubleshooting.

Two last driver performance items that Parlier recommends: "For a small price in cost and weight, treat your drivers to Kenworth's Extended Day Cab and Kenworth QuietCab(R) package. The Extended Day Cab gives the driver 6 inches more room fore-and-aft, and 5 inches more headroom, and the QuietCab option reduces in-cab noise by two decibels, meaning it cuts perceived noise by almost 50 percent. These options can dramatically reduce driver fatigue, and that helps keep them more productive."

Read more in Paul's Fleet Factors column: 2010 Emissions Report Card