Creating a vocational truck is akin to updating an older kitchen. While the plan might seem simple—requiring cabinets, appliances, wiring, and plumbing—the reality often involves uncovering structural challenges, outdated wiring, regulatory issues, and space limitations that necessitate ongoing compromises.
In the same vein, a service body is not merely attached to a chassis. Considerations such as weight distribution, tool cabinet placement, electrical loads, axle spacing, and frame clearances all interact with each other. Changing one aspect can require adjustments in multiple other areas.
After making changes, many fleets lack the luxury of reworking the truck. It’s crucial to get everything right from the onset.
With today’s technology, it is both feasible and intelligent to design the truck virtually prior to ordering the body and chassis. Many body builders and truck equipment manufacturers (TEMs) rely on CAD software and tools like Load Expert or Truck Science to plan weight distribution, axle configurations, and component placements before production begins. This allows for adjustments on-screen to optimize specifications and ensure compatibility with chosen chassis.
Potential Issues
As Shakespeare wisely noted, “There are more things in heaven and earth than are dreamt of in your philosophy.” While installing simpler features like dump bodies is generally straightforward, complexities arise with advanced chassis configurations featuring PTOs and extra axles, significantly increasing the risk of issues.
Nicolas Picard, technical manager at Excellence Peterbilt, shared an incident where a body installer rerouted an exhaust stack to accommodate a second steer axle, unaware of how it would interfere with the aftertreatment system. This mistake led to three complaints about a malfunctioning NOx sensor, which was ultimately caused by rainwater entering the rerouted exhaust. Such solutions could have been more effective if the installer had sought advice first.
Avoiding Communication Breakdown
Miscommunication can lead to costly mistakes, especially when customers acquire stock or used trucks without confirming compatibility for their intended bodies. When body builders fail to provide accurate weight information to dealers, it complicates ensuring appropriate load percentages on axles post-installation.
Jamie Impola from Rush Truck Centres noted that even minor changes—like extending the length of a dump box—affect weight distribution and crossmember locations, creating substantial risks if overlooked. The best practice is collaborative communication among the customer, dealer, and body builder to ensure alignment throughout the process.
Evolving Wiring Standards
A new challenge in vocational truck building is multiplexing, a system where a single wire can transmit multiple signals. While larger equipment manufacturers have adapted to this, smaller builders often lag behind in electronic control integration. Effective communication among electronic components is vital, especially when conventional wiring practices are mistakenly employed.
Sean Whelan, a Mack vocational sales manager, noted that although older standards like a 9-pin connector are still in use, the industry is shifting towards multiplexed systems. As proprietary multiplex architectures evolve within different truck manufacturers, body builders must familiarize themselves with these changes—something that many are already starting to do. OEMs are providing training and even engineering access for body builders to help them navigate this transition better.
