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How to Choose a Fuel Tank Toolbox Combo

Fuel Tank Toolbox Combo in Pickup Truck

Choosing a fuel tank/toolbox combination is a matter of balancing your personal preferences and the layout of your truck bed.

There are several key considerations to bear in mind to ensure you select the right unit to meet your needs. With a range of sizes, shapes, and upgrades available, there are more than enough options to find the right design for you. 

Bed Space

The first step is to determine how much space you have available in the bed of your truck. Measure the width, length, and height at the end closest to the cab.

Once you have your measurements, add an inch of additional space to ensure there’s enough flex for a proper fit.

  • Capacity: The amount of bed space you have will determine whether your truck can accommodate larger models with a higher tank capacity. Tanks that fit up and over the lip of the bed can hold as much as 110 gallons of fuel, while smaller designs may only hold 28 gallons.
  • Length: The most common dimensions for length are roughly 60 inches on top and 50 inches along the bottom. Tanks that extend over the side of the bed can reach up to 70 inches.
  • Width: Compact tank and toolbox combinations start at approximately 12 inches wide, which leaves plenty of bed space for other equipment or materials. Large units and sloped wedge models can be as wide as 20 to 30 inches.
  • Height: Most tanks fall within the range of 15 to 20 inches. Taller styles that sit above the bed rail can exceed 26 inches.


Fuel tank toolbox combos will have less fuel capacity than a standard transfer tank. The size of the toolbox directly influences how much left over space is available for the fuel tank.

Browse tank toolbox combos by fuel capacity:

Tank and Toolbox Combo Size Guides

After you have measured the available space in your pickup, the next step is to match your available space with the tank & toolbox options that most closely fit your space requirements. The following size guides are designed to help you quickly find tank options that match your available space.

Styles and Shapes

Although rectangular models are the most common, fuel tank/toolbox combinations are available in multiple styles and shapes. The placement of the toolbox portion also varies, so it’s possible to have two units with the same outer dimensions but drastically different interior styles.

Possible shapes and styles include:

  • Rectangular models that taper toward the bottom.
  • Low Profile Fuel Tank Toolbox Combo with lower tank height.
  • L-shaped tanks with a taller rear portion and a smaller front section.
  • T-shaped tank and toolbox combinations that fit over the bed rail.
  • Under Tonneau Tank Toolbox Combo.
  • Truck Tool Box Combos for Short Beds.
  • Wedge models with a triangular toolbox in front and a rectangular tank in the back.

Auxiliary Fuel Systems

Auxiliary Fuel Tank Toolbox combos provide a supplementary fuel tank that connects directly to your factory gas tank. These options typically require factory gas tanks that work with diesel fuel.

Some designs are more sophisticated than others, and simpler models will require more input from you as you drive to transfer fuel from the auxiliary tank into your vehicle.

The Fuelbox has a proprietary system known as the Auto Fuel Controller (AFC). The AFC is fully automated, so there’s no need to watch a gauge or push a button. The controller senses when your tank is getting low and transfers diesel from your combination fuel tank and toolbox into the main factory tank.

ATTA has developed two systems to suit a broader range of needs. The Push N Fuel controller requires manual input to function. You press and hold a switch to transfer fuel from the auxiliary tank when you notice that your truck’s tank is running low. The Freedom Fill Auxiliary System resembles the AFC and automatically moves fuel as needed.

Accessories and Upgrades

Many combined fuel tank toolboxes can be built with optional upgrades for an additional cost. A few of the most popular accessories include:

  • Interior and exterior black spray liner.
  • Tank-mounted fuel gauges.
  • Supplemental transfer pumps.
  • Locking gas caps.
  • Bed steps to reach the toolbox from the side.
  • Diamond plate finishing.
  • Tie-down bars.

For additional ideas, see our article on the best fuel tank toolbox combos.


There are multiple brands that provide high quality fuel tank toolbox combos.  Some of the most popular brands include:

  • ATTA Tank
  • ATI Tank
  • The Fuelbox
  • Transfer Flow

ATTA Tank is located in Fort Worth, Texas. This manufacturer’s combination tanks and toolboxes can hold 33 to 110 gallons of diesel. Most models are rectangular, and some can fit under covers. ATTA Tank does not make combination units that fit over the bed rails, but they do have a unique wedge model and a designated unit for short-bed trucks with covers.

ATI Tank is headquartered in Winter Haven, Florida. Its combination units consist of a 30-gallon and 65-gallon model with a rectangular shape. ATI Tank stands out from the competition because it accepts custom orders for fuel tank/toolbox combinations, and it also offers a separate product line for gasoline-powered trucks.

Transfer Flow is based in Chico, CA and offers fuel tank toolbox combos that include transfer tanks or auxiliary fuel tanks.  The auxiliary fuel tank toolbox combos include an advanced TRAX 4 operating system that automatically transfers fuel into your factory based fuel tank. 

Transfer Flow’s advanced system is controlled by an app that allows you to monitor the status directly from your phone. Transfer Flow’s app works with both Apple and Android phones.

The makers of The Fuelbox are based in Visalia, California. This vendor specializes in traditional rectangular models, but it also produces designs that fit over the bed rail or under a cover. Capacities range from 28 to 95 gallons for diesel only.