There are a variety of factors that affect truck performance. Chief among these are vehicle configuration, total vehicle weight, vehicle cruising speed, trailer type, trailer gap, tire type and driver driving habits. Consequently, there is no single drivetrain solution.
However, critical to any truck's productivity and lifecycle costs - residual values, fuel economy improvements, reduced maintenance, decreased driver training, etc. - is the proper spec'ing and maintaining of the drivetrain.
Basically, the drivetrain, also referred to as the powertrain or powerplant, is composed of a group of components that generate power and deliver it to the road surface to make the vehicle move. All the components must be compatible, otherwise, vehicle performance is not going to be optimized. When drivetrain components don't work in harmony, there can be premature component wear and failures, resulting in increased vehicle downtime and maintenance costs.
Proper spec'ing and maintaining of the drivetrain begins with having a complete understanding of the vehicle's intended application and operation. Vehicles should not be mixed in applications. A two-axle pickup and delivery truck cannot perform the same duties as a tandem-axle truck spec'd to haul construction materials, for example. A long-haul truck spec'd to operate in the flat Midwest will not perform well in mountainous terrain or as a city delivery vehicle. Fire apparatus needs high horsepower and torque, whereas a city pickup and delivery vehicle doesn't.
A lot of frustration can be avoided by using the right truck for the right job.
For proper component specification, the truck dealer and the original equipment manufacturers (OEM) must know the truck's purpose and application, including maximum loads; maximum grades; road surface, terrain, routes and operating environment; duty cycles; annual mileage; and percent of load going versus returning. Also important are the details of the truck specifications, such as make, model, height and width, and gross axle weight rating, gross combination weight and gross vehicle weight.
Truck dealers and OEMs also need to know desired road speeds (maximum and cruising), engine horsepower and torque, tire specifications, transmission ratios and step sizes and axle ratios.
The three key factors in drivetrain specifications are startability, gradeability and fuel economy, all of which are impacted by the aforementioned factors.
Engine suppliers and truck OEMs have software tools and simulation programs to help improve drivetrain performance. Components ought to be checked for compatibility. This will prevent trucks from being built with axle ratios or transmission gearing that is not ideal for the intended application.
To get some guidance on engines and drivetrains, Fleet Maintenance Magazine visited with officials at ArvinMeritor. Headquartered in Troy, MI, ArvinMeritor is a premier global supplier of a broad range of integrated systems, modules and components to the motor vehicle industry. The company serves commercial truck, trailer and specialty OEMs and certain aftermarkets.
Be sure to understand the specific application and vocation of each vehicle, stress the ArvinMeritor officials. The right components need to be selected from the start. Components that are not properly matched will not work efficiently together to produce the desired performance and economy.
What's more, trucks spec'd with components that do not fit the vocation and application the truck will be used in will undoubtedly end up with costly repairs and downtime in the future, they say.
High grades and poor road surfaces, gross combination weights, quantity of start/stops, etc., all impact a vehicle drivetrain's performance and life. It does no good to save a few dollars up front by underspecing components, point out the officials, because these components will fatigue, causing the truck operator to pay for them in downtime and repairs later.