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Popular Transfer Flow Products

Transfer Flow makes a wide variety of tank options. Below are some of the most popular.

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Which Transfer Flow Tank Do You Need?

Transfer Flow makes three fundamentally different types of fuel tank systems. Getting this right before you order is the most important step — they solve different problems for different operators.

  • Auxiliary Tank — Sits in the bed, automatically transfers diesel to your main tank while you drive. Extends driving range without driver input. Diesel only. TRAX 4 computer-controlled.
  • Transfer / Refueling Tank — Sits in the bed, manual dispensing via 12V pump and hose. DOT-legal for carrying and dispensing gasoline, diesel, and kerosene. For refueling your equipment or other vehicles in the field — not for auto-transferring to your main tank.
  • Replacement Tank — Installs in the factory location under your truck. Replaces your stock tank with a higher-capacity unit. No bed space used. Available for select Ford F-150 and F-250/350 applications.
  • Tank + Toolbox Combo — Combines either an auxiliary or transfer tank with a built-in locking toolbox compartment. TRAX 4 controlled on auxiliary versions. 40-gallon and 70-gallon configurations available.

About Transfer Flow

Transfer Flow was founded in the spring of 1983 in Chico, California by Bill Gaines — a former General Motors engineer — and his wife Jeanne, with five employees. The company started as an OEM fuel system supplier to the motorhome and travel trailer industry, then expanded into mobility, work truck, and mainstream automotive markets as demand grew. By 1994, continued growth required relocating to a 35,000-square-foot manufacturing facility; a 20,000-square-foot addition followed in 2000, and a 15,000-square-foot warehouse was added in 2008. Today, Transfer Flow operates from a 70,000-square-foot facility in Chico and employs more than 100 people from across Northern California, with a distribution warehouse in Tennessee.

Transfer Flow has been a member of the National Truck Equipment Association (NTEA) for over 37 years. Ben Winter, the company's Director of Business Development, currently serves as Chairman of the NTEA — the leading association supporting the work truck industry, representing more than 2,000 member companies. Transfer Flow is also the industry's only manufacturer to develop and patent a computer-controlled auxiliary tank operating system: the TRAX 4, now in its fourth generation, which uses AutoTrans® technology to manage automatic fuel transfers without driver input.

Every Transfer Flow tank system is designed, engineered, and manufactured in the United States from American-made steel. The company uses what it calls ReliaSteel® — high-yield US aluminized steel — with robot-welded seams (not spot-welded) that provide structural integrity significantly beyond lower-cost alternatives. All gasoline replacement tank systems have been tested and granted Executive Orders from the California Air Resources Board, making them legal in all 50 states.

The TRAX 4 System — How It Works

Every Transfer Flow auxiliary tank system includes the TRAX 4 patented computer-controlled operating system. Here's what it actually does:

TRAX 4 monitors the fuel level in your factory main tank continuously while the truck is running. When the main tank drops to a predetermined threshold — based on the capacity of your specific main tank and auxiliary tank — the system automatically activates the transfer pump and moves fuel from the auxiliary tank into the main tank. When the main tank reaches a safe fill level, the transfer stops. The driver doesn't flip a switch or monitor anything. Fuel just appears in the main tank as needed, and the factory fuel gauge reads normally throughout.

The TRAX 4 mobile app connects to the system and displays real-time fuel levels in both tanks on your phone, along with pump status ("PUMP ON" during a transfer). An optional LCD in-cab monitor is available for buyers who prefer a dedicated display over the app. The LCD shows the auxiliary tank level as a bar graph that decreases as fuel transfers out.

TRAX 4 applies exclusively to auxiliary tank systems and auxiliary tank/toolbox combos. Transfer/refueling tanks are manual systems — TRAX 4 does not apply to those products.

Transfer Flow by Truck Model

Transfer tanks (refueling) work with any truck regardless of diesel or gasoline engine. Auxiliary tanks require diesel. Replacement tanks are vehicle-specific — contact our team to confirm availability for your year, cab, bed length, and engine.

Frequently Asked Questions — Transfer Flow

What is the difference between a Transfer Flow auxiliary tank and a transfer tank?

An auxiliary tank automatically transfers diesel to your main factory tank while you drive — controlled by the TRAX 4 system. You do nothing; fuel moves on its own. Diesel only. A transfer tank is manual: you pump fuel from it to another vehicle or piece of equipment using the included 12V pump and hose. Transfer tanks are DOT-legal for gasoline, diesel, and kerosene. The short version: auxiliary tank = more range for your truck. Transfer tank = mobile refueling station for your equipment.

What is the Transfer Flow TRAX 4 system?

TRAX 4 is Transfer Flow's patented computer-controlled system for auxiliary tanks. It uses AutoTrans® technology to automatically transfer fuel from your auxiliary tank into your main tank at predetermined fuel levels while driving. Includes an LCD display showing both tank levels. The free TRAX 4 app lets you monitor both tanks from your phone. TRAX 4 applies to auxiliary tanks and aux tank/toolbox combos only — not transfer tanks.

What is a Transfer Flow replacement fuel tank?

A replacement tank installs in the factory location under your truck — replacing the stock tank with a higher-capacity unit. No bed space used. Your fuel gauge reads accurately. Available for Ford F-150 (gas), Ford F-250/350 (gas and diesel), and select other trucks. Gasoline versions are CARB Executive Order-approved, making them 50-state legal. Contact us to confirm fitment for your specific truck.

What size auxiliary tank should I get?

The 40-gallon is the most universally compatible — fits half-tons, RamBox trucks, 5th-wheel prep trucks, and utility beds. The 37-gallon fits under retractable canister tonneau covers (Pace-Edwards, Truck Covers USA). The 50-gallon fits most full-size trucks under standard tonneau covers. The 75-gallon requires a long-bed truck. Confirm your bed length, any tonneau cover, and bed accessories before ordering.

Are Transfer Flow tanks legal to carry gasoline?

Transfer tanks carry a DOT Special Permit that makes them legal in all 50 states for carrying and dispensing gasoline, diesel, ethanol, methanol, and kerosene. Auxiliary tanks are diesel-only and not for dispensing. Gasoline replacement tanks have CARB Executive Orders for 50-state emissions compliance. If you're in California, confirm the specific product's compliance before purchasing.

What trucks does Transfer Flow fit?

Auxiliary and transfer tanks fit most full-size pickups: Ford F-150, F-250/350, Chevrolet/GMC Silverado/Sierra (all generations), RAM 1500/2500/3500, and Toyota Tundra. The 40-gallon also fits mid-size diesel trucks (Chevrolet Colorado and GMC Canyon diesel). Replacement tanks are vehicle-specific. Always confirm bed length, cab, and engine type before ordering — contact our team if unsure.

Can I install a Transfer Flow tank myself?

Yes. Every Transfer Flow system ships with comprehensive step-by-step instructions and every component needed for installation, including all hardware and zip ties. Installation videos are on Transfer Flow's YouTube channel. In-bed auxiliary and transfer tanks are the most straightforward DIY installs. Replacement tanks require working under the truck and are better suited to buyers comfortable with mechanical work; professional installation is recommended if you're not.

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