A service truck is judged on one thing: whether the job gets finished without a second visit. Every storage decision on it should be measured against that, which produces a very different layout from a truck that simply carries tools to a workshop.
What Makes a Service Truck Different?
It has to carry the parts as well as the tools. A contractor's truck can go back to the shop for a fitting. A mobile service truck that has to do the same has already failed the call, so the layout is built around carrying more variety in less space and finding it quickly.
Compartments Beat One Big Space
Underbody boxes along the frame give you a run of separate compartments at working height, each one dedicated to a category. That separation is the whole point: you go to a door rather than searching a volume.
- One compartment per category, kept the same on every job.
- Frequently used items at the driver side rear, where you park to work.
- Heavy items low and near the axle rather than at the tail.
- One compartment left deliberately empty for the job in progress.
The empty compartment is not wasted space. It is where a partly dismantled assembly goes when the customer needs the driveway back.
Keep the Deck Clear
The flat area above the compartments is the most valuable surface on the truck, and it disappears the moment it becomes storage. Keep it clear as a working surface and a place to set parts down, and put the storage below the deck line where it belongs.
A chest box is the exception worth making, since it can be secured to the deck and removed when the space is needed.
Protect the surface while you are at it. A deck used as a bench collects gouges from the first month, and a replaceable mat or a sacrificial board costs far less than refinishing it later.
Power, Air and Light
Anything that needs power on site should have a fixed home rather than travelling in a compartment. That means a mounted compressor, a generator or an inverter, wired properly on its own protected circuit and secured against movement.
Work lighting is the detail most often left until later and most missed in winter. Racks and cab protectors give you somewhere to mount rear facing work lights without drilling the body.
Long Material and the Cab
If the work involves pipe, conduit or stock, a rack over the deck keeps it off the working surface entirely, and a headache rack stops anything sliding forward into the cab. Both mount above storage rather than competing with it.
See underbody tool boxes, chest boxes, racks and headache racks.