How to Add a Cab Pass-Through to a Box Truck

One of the functional upgrades you can make in a box truck is to create a pass-through between the vehicle cab and the cargo box. This modification provides many benefits.  These benefits include easy access between areas, better climate control or added security.

Box truck normally does not have this pass-through feature.  The question is, it possible to add one?

The answer is yes.  However, how it is created make a big difference. What I hope to do here is provide ideas that will make this possible.

The Challenge: Box Trucks Don’t Have Walkthroughs

Box trucks are normally used to haul cargo.  But in the case of a walkthrough the box may serve a different purpose.  These uses could be creating a living space or a mobile workshop. In these instances, a walkthrough is very functional.

The first issue in making this conversion is that the cab and box are separated by a solid wall. The next thing to note is the box is separated by a gap leaving a space between the cab and box. In rare cases is the box mechanically attached.  Filling the gap is one issue that needs to be addressed.

Here are the most common concerns builders need to solve:

• Cab and box movement – The reason that the box is not attached directly to the cab is because while traveling there is flex between the cab and the box. If the box were rigid it would cause cracking and stress on the vehicle.
• Filling the gap – Once the opening for the pass through is cut the vehicle is exposed to rain, wind, and dust. There needs to be a way to seal it from the elements.
• Access – Having access from inside the vehicle can provide some utility as you do not need to go outside to move between spaces. This is a huge benefit during bad weather or if you are in an urban environment.

Common DIY Approaches (And Their Drawbacks)

When adding a pass-through, most builders look at a few options:

1. Cutting a Crawl-Through

An opening between the cab and the box allows basic access, but it need a way to fill the opening and the gap —especially since the cab and box flex independently.

2. Installing a Custom Door

Some go all-in and install access doors. This requires new framing in walls. Fabricating a door. This is functional, but labor-intensive and can be quite expensive.  

3. Using Soft Materials

Materials like neoprene or fabric are sometimes used to bridge the gap.  These options require a lot of skill to fabricate.  These materials can be affected by weather over time.

So what’s the best solution?

The Better Way: Use an Accordion Rubber Boot

One of the most popular and effective ways to accomplish the goal of sealing and filling the pass though is installing a rubber accordion boot.  This item is used frequently in sleeper cab trucks, camper shells and expedition vehicles.

Why It Works:

• Flexibility – The accordion bellows design expands and contracts with vehicle movement. This makes it a great choice for setups where the cab and box aren’t rigidly connected.
• Weather Resistance – It is made with EPDM rubber and forms a tight seal to block out wind, rain, dust, and road grime.
• Simple Installation – Once the opening is cut, the boot can be trimmed to size and clamped or mounted in place. Note: the design requires a thin wall or flange to attach the boot. Sometime a mounting plate may be required on the cargo box.
• Durability – Designed specifically for vehicle use, these boots are manufactured to last many years of road travel.

Whether you’re creating a small crawl-through or a full walk-through, an accordion boot provides a clean, professional-looking seal that solves the biggest challenges cargo box truck converters face.

Planning Your Pass-Through Build

Here are some basic tips to keep in mind:

• Make sure the cab and box openings are properly aligned and the exact same size before installation.
• Use solid mounting surfaces on both ends (cab wall and box wall).
• Choose an accordion boot made from EPDM rubber, which is UV resistance and flexibility for a wide range of temps.

Where to Get an Accordion Boot

Accordion boot kits are available in multiple sizes and configurations, depending on your build.  We offer a variety of flexible rubber seals to match your projects requirements.

Final Takeaway

Adding a pass-through to a box truck is possible and practical. The key to a successful build is using a solution that works best for you. There are many ways to accomplish the walkthrough. but one solution that have worked many people is the accordion boot. This is one of the best methods to create a clean, functional, and weather-tight pass-through between your cab and cargo box.