Operators who don’t need that high of horsepower or torque can spec the Cummins ISL G engine, which is rated at 320-hp and 1,000 lb-ft of torque. The ISL G engine operates on either LNG or compressed natural gas (CNG). It uses a maintenance-free, three-way catalyst and is 2010 EPA- and CARB-compliant without the use of SCR technology or a DPF.

“Deciding on whether to go with CNG- or LNG-powered trucks may be determined by the availability of the fuel in your area,” Parlier says. “With many local transit and government agencies using compressed natural gas to power buses and trucks, sources of CNG fuel may be easier to find in some areas than LNG.”

Operators should also consider that fueling CNG-powered trucks doesn’t require special training as it does with LNG trucks, she adds. However, LNG fuel has a higher energy density than CNG since it is a liquid, so an LNG-powered truck can go further on the same amount of fuel.

Neither LNG nor CNG has the high energy density of diesel fuel, but both are cleaner fossil fuels, so they produce less carbon pollution than diesel fuel. Also, both are domestically produced, so they have the potential to reduce reliance on foreign oil. The drawback can be a significantly higher cost engine, Parlier says. But some state and local air quality control agencies may have limited programs with grants to help offset the additional cost of the engine technology. Plus, by deleting the additional weight associated with the SCR or EGR emission control systems, a natural gas-powered truck may be able to carry more payload.

Load and hauling questions

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,” 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.”

The Drivetrain

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 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 more than times as long as a single 11-inch underhood air cleaner before needing replacement.

Weight watching

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.”