Spec Features to Reduce Abuse

Spec'ing a truck correctly for the job goes a long way toward preventing abuse. "The proper selection of transmission and axle ratio plays a huge role in reliability," says Ivan Neblett, Freightliner Trucks. "For manual transmissions, having the proper low gears married with the proper axle is very important."

The truck must have the right gearing to start the load moving and traverse jobsite grades. "Transmission ratios and rear axle ratios are very important in terms of the gradeability of the truck," says Melissa Gauger, International Trucks. "If the ratios are not spec'd for on/off-highway, the truck may have problems driving in quarries or on jobsites."

The engine should operate at its "sweet spot," as well. "You want to be operating the engine at its most efficient rpm if at all possible and not putting undue stress on the engine, clutch, transmission and rear axle," says Curtis Dorwart, Mack Trucks. "The selection of transmission gearing and ratios, [plus] the rear axle ratio, can make the difference between getting the load going from a stop or not, as well as how effectively the load is going to go up the hill once moving. If you don't get a good balance between all of the factors, you could have a situation where the truck will not be able to haul the load at all, or haul it so slowly that productivity is severely compromised."

Also consider the best transmission for the conditions. "Automatic transmissions do very well in off-road applications," says Neblett. "It takes drivers out of the equation of knowing when and how to shift properly and provides more compensation to get through those conditions. Automatic transmissions also do really well in saving the drivetrain."

And don't forget traction options to boost performance. "There are also options that can be specified on the truck to gain the best traction off road, including differential locks and front and rear axle locks," says Neblett.