Rear suspensions on heavy haulers have historically been mechanical types, but air suspensions are also popular.
"The ride is better and you have more operational flexibility," said Parlier. "By lowering the air suspension, a driver can back under and pick up a lowboy trailer instead of using skid ramps and ramming into the trailer in order to couple it to the tractor."
Kenworth offers different versions of its eight-bag air suspension to suit different applications. The AG460 is commonly used for 46,000-pound tandem axle configurations, and the AG690 can be used for tri-drive applications. The company will still mount skid ramps on the end of the frame for heavy haulers who elect to use them.
The approach to spec'ing transmissions for heavy haulers is similar to that of power: the more, the better. In this case it's ratios.
Heavy haulers typically choose an 18-speed manual. But in very heavy applications, options include a two-speed auxiliary transmission or two-speed rear axle. In both cases, they double the number of available ratios, allowing improved startability and driveability. A two-speed auxiliary transmission will double the reduction, while a two-speed rear axle will increase the reduction by a third.
"A two-speed axle works well up to about 190,000 lbs. GCW, but above that I'd recommend an auxiliary transmission," Parlier said.
Finally, look at driver performance-related items that can help gain operational efficiencies.
Since heavy haulers often deal with large, oversize loads, look at specifying as much glass area as possible and plenty of mirrors, Parlier said. "Four-way adjustable, cowl-mounted mirrors can be complemented with convex mirrors. The cowl mounting helps because the mirrors are not subjected to countless door slams and stay in adjustment longer than door-mounted types."
She suggests picking low-replacement cost windshields, when available. "Most vocational fleets replace at least one windshield side per truck annually. Two-piece flat-glass windshields with roped-in seals can be replaced in 30 minutes for less than a hundred dollars, which can save thousands of dollars over the truck's life," he said.
An extended day cab might be the right choice for heavy haulers that do not need a sleeper, but are still looking for a little extra room in the cab. Kenworth's Extended Day Cab enhances driver comfort with an additional 6 inches of length and 5 inches of cab height compared to its traditional day cab. And for a quieter driver's office, the QuietCab(R) sound insulation package reduces in-cab noise by two decibels.
To enhance truck productivity and the driving experience, consider adding a navigation system like the NavPlus(TM), Parlier advised. It offers true truck navigation by Garmin, communication, diagnostics, and infotainment technologies. The system is also fully compatible with the Electronic Service Analyst (ESA), a computer-base diagnostics tool, which simplifies troubleshooting.