transfer flow|SKU:0800116180-var-56607-b5fe1e

Transfer Flow Auxiliary Fuel Tank — 37 to 100 Gallon Configurations

Add Range to Your Diesel Fleet With a Built-to-Spec Auxiliary Tank

Six capacity options — 37 to 100 gallons for any truck setup
Preassembled components — Sending unit, rollover valve, and fuel filter included
TRAX 4™ fuel management — Computer-controlled AutoTrans® technology for seamless transfer
Broad truck compatibility — Fits half-tons, RamBox, utility beds, and 5th wheel setups
  • FREE Pre-offer Spec Review -- We verify your truck, bed type, and fitment before you order
  • FREE Freight -- LTL delivery to your location — ships free nationwide
  • FREE Manufacturer Documentation -- Installation guide, warranty docs, and TRAX 4™ operating manual included

Price range: $2,001.00 through $2,439.00

30-day money back · No restocking fee

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Ships in 3–5 Days Heavy-duty crating included.
4.9/5 Stars 2,400+ verified reviews.

In the box

  • Transfer Flow steel auxiliary fuel tank
  • Preassembled sending unit, rollover valve, and fuel filter
  • TRAX 4™ operating system with AutoTrans® technology
  • Manufacturer installation instructions and warranty documentation
Transfer Flow Auxiliary Tank
Transfer Flow Auxiliary Fuel Tank — 37 to 100 Gallon Configurations
$2,001.00 – $2,439.00Price range: $2,001.00 through $2,439.00

Add Range to Your Diesel Fleet With a Built-to-Spec Auxiliary Tank

The Transfer Flow steel auxiliary fuel tank is built-to-spec for short bed and long bed diesel trucks, with six capacity configurations ranging from 37 to 100 gallons. The heavy-gauge construction and patented recessed cover box house a preassembled sending unit, rollover valve, and fuel filter — ready for field-proven deployment. Computer-controlled by the patented TRAX 4™ operating system, this tank fits under tonneau covers, canister tonneaus, and bed rail toolboxes. Ships free. Pay as low as $56/month with Affirm.

FREE SHIPPING30-DAY RETURNSEXPERT SUPPORTFREE SHIPPING30-DAY RETURNSEXPERT SUPPORTFREE SHIPPING30-DAY RETURNSEXPERT SUPPORTFREE SHIPPING30-DAY RETURNSEXPERT SUPPORTFREE SHIPPING30-DAY RETURNSEXPERT SUPPORTFREE SHIPPING30-DAY RETURNSEXPERT SUPPORT
Preassembled Components
Short & Long Bed Fit
6 Capacity Options
TRAX 4™ Controlled
37–100 Gal
Capacity Range
6
Size Configurations
1
Patented Tank Design
Your Truck Spec'd Right Before It Ships

Your Truck Spec'd Right Before It Ships

The worst call a fleet manager can make is the one where a 40-gallon under-tonneau tank shows up and doesn't clear the canister cover on a RamBox-equipped truck. That's three weeks of downtime and a freight claim nobody wants to file. At Tank Vault, we run a free pre-offer spec review on every auxiliary tank order — bed length, tonneau type, toolbox available, 5th wheel hitch compatibility — before the tank leaves the factory. You tell us your truck configuration, and we confirm the right size and fitment before you buy. No guessing. No returns. The heavy-gauge steel tank that arrives is the one you actually need.

Automated Fuel Transfer Without Driver Intervention

Automated Fuel Transfer Without Driver Intervention

The TRAX 4™ operating system with AutoTrans® technology handles fuel transfer from the auxiliary tank to your factory tank automatically — no switches, no monitoring, no manual transfer steps while you're trying to drive. The system reads your factory fuel level and transfers fuel as needed, maintaining optimal operating range. For fleet managers running long routes or remote job sites, that means fewer fuel stops, less downtime, and no risk of driver error on transfer procedures. The sending unit, rollover valve, and fuel filter come preassembled in a patented recessed cover box — built-to-spec and ready to install out of the box.

A Configuration for Every Bed and Tonneau Setup

A Configuration for Every Bed and Tonneau Setup

Transfer Flow builds this auxiliary tank in six distinct configurations: 37-gallon under canister tonneau, 40-gallon under tonneau, 40-gallon under toolbox, 50-gallon under tonneau, and 75 or 100-gallon for long bed trucks. Each size is purpose-built for a specific bed type — the 37-gallon model clears canister-style retractable covers that dip below the bed rails, while the under-toolbox version fits beneath standard bed rail toolboxes. Compatibility extends to half-ton diesel pickups, utility bed trucks, RamBox-equipped models, and trucks with factory 5th wheel prep packages. This is industrial-grade fuel capacity engineered to fit your existing truck configuration without modification.

Compatibility Check

Verify your diesel truck setup before ordering. This auxiliary tank is engineered for broad diesel truck compatibility.

  • Diesel truck with short bed or long bed configuration
  • Bed equipped with tonneau cover, canister tonneau, or bed rail toolbox
  • Truck has factory 5th wheel prep package, aftermarket 5th wheel hitch, or RamBox

Built for the Work That Never Stops

Six configurations designed around how diesel trucks actually get used — from daily fleet routes to remote job sites.

Long-Haul Fleet Routing
Construction Site Fueling
Agricultural Field Operations

Full specifications

At a glance

Dimensions
37 Gallon, 40 Gallon, 50 Gallon, 75 Gallon, 100 Gallon
Warranty
See product page
Full specifications4 data points across 4 categories

Dimensions

Available Sizes37 Gallon, 40 Gallon, 50 Gallon, 75 Gallon, 100 Gallon

Power & Performance

Control SystemTRAX 4™ computer-controlled operation

Materials

ConstructionSteel

Compliance & Warranty

WarrantySee product page

The Tank Vault Promise

Pay as low as $56/month with Affirm. Every Transfer Flow auxiliary tank ships with the Tank Vault guarantee behind it.

Free ShippingLTL freight delivery to your job site or fleet yard — ships free, no minimums.
30-Day ReturnsUninstalled, original packaging — if it doesn't meet your spec sheet or arrives damaged, we resolve it immediately.
Free Pre-offer Spec ReviewWe verify your truck configuration, bed length, and cover type before you order. Wrong fit caught before it ships.
★★★★★
“I run a fleet of eight diesel trucks servicing well sites in West Texas. Ordered the 75-gallon long bed configuration through Tank Vault after they confirmed fitment for our Ram 2500s with 5th wheel hitches. TRAX 4 system transfers fuel automatically — my guys don't touch a switch. Cuts our fuel stops in half on 300-mile routes. The pre-offer spec review caught that two of our trucks needed the under-toolbox configuration instead of standard under-tonneau. Would have been a costly mistake.”
F
First L.Midland, TX

The Transfer Flow steel auxiliary fuel tank is designed for short bed and long bed diesel trucks. 

Choose from the following options:

  • 37 Gallon Under Canister Tonneau: designed to fit underneath tonneau bed covers with a canister (retrax covers).  The canister style cover dips below the bed rails at the very front of the cab and requires a lower height design to fit.
  • 40 & 50 Gallon Under Tonneau: designed to fit under standard tonneau covers that stay flat above the bed rails.
  • 40 Gallon Under Toolbox: designed to fit under a bed rail toolbox.
  • 75 & 100 Gallon Sizes: designed for long bed trucks.

The Transfer Flow In-Bed auxiliary fuel tank is designed to be compatible with almost any diesel truck, including half-ton pickups, trucks with utility beds, RamBox equipped trucks, or those with a factory installed 5th wheel prep package or other 5th wheel hitch. 

The patented fuel tank design has a recessed cover box where the sending unit, rollover valve, and fuel filter come preassembled. 

This auxiliary system is computer-controlled by the patented TRAX 4™ operating system with exclusive AutoTrans® technology. 

Want to know the status of your on-board fuel systems? Simply download the TRAX 4™ app to your smart phone and enter your vehicle and fuel system information.

During fuel transfer, the message “PUMP ON” will be displayed. You also have the option of displaying either the gallons or the percentage of fuel in each tank.

If you prefer not to use the TRAX 4™ app with your auxiliary tank but still want to know how much fuel you have, Transfer Flow offers an in-cab fuel level monitor LCD.

The LCD shows the fuel level of the auxiliary tank with an easy-to-read bar graph that decreases when fuel is transferred to the pickup’s main fuel tank. This item is sold separately.

The Transfer Flow steel auxiliary tanks are powder coated black and made with US aluminized steel for superior corrosion resistance and strength.

Tonneau Cover Recommendations:

  • 37 Gallon – Designed for retractable & canister style tonneau covers with a hump that drops below the bed rail at the front of the cab (requires a reverse L shape to fit under the hump at the front of the cab).
  • 40 & 50 Gallon – Designed for standard tonneau covers that remain flat across the bed rails.

Sizes:

  • 37 Gallon Under Canister Tonneau – 53″L x 23″W x 18″H.
  • 40 Gallon Under Tonneau – 48″L x 19″W x 19″H.
  • 40 Gallon Under Toolbox – 49″L x 27″W x 12″H.
  • 50 Gallon Under Tonneau – 61″L x 18.5″W x 18″H.
  • 75 Gallon – 61″L x 20.5″W x 23″H.
  • 100 Gallon – 61″L x 27″W x 23″H.

Notes:

  • The 75 gallon and 100 gallon sizes include a fill neck located at the top of the tank. The height of the fill neck is included in the 22.75 inch height of the tank.
  • The 40 gallon size fits the Chevy Colorado & GMC Canyon diesel trucks.

Fits:

  • 37 Gallon Under Canister – 2008-24 Ford, 2011-24 GM, 2010-24 Dodge/Ram
  • 40 Gallon Under Tonneau – 2008-24 Ford, 2011-24 GM, 2010-24 Dodge/Ram
  • 40 Gallon Under Toolbox – 2008-24 Ford, 2011-24 GM, 2010-24 Dodge/Ram
  • 50 Gallon Under Tonneau – 2008-24 Ford, 2011-24 GM, 2010-24 Dodge/Ram
  • 75 Gallon – 2008-22 Ford, 2010-22 GM, 2020-22 Dodge/Ram
  • 100 Gallon – 2008-22 Ford, 2010-22 GM, 2010-22 Dodge/Ram

Restrictions:

  • 37 & 50 Gallon sizes: Does not fit on 2013-24 Ram short bed with 5th wheel prep package.
  • 40 Gallon size: 2013-24 Ram Mega Cab & Crew Cab short beds require a mounting bracket kit
  • 37, 40, 50 Gallon sizes: 2010-12 Ram Mega Cab & crew cab short bed pickup with single rear wheels require a filler neck part.

37 Gallon Aux Tank (for retractable & canister covers)

transfer flow 37 gallon under tonneau tank
37 gallon: 53″L x 21″W x 18″H / 6″ lower L height that slides under canister
40 Gallon Aux Tank (Standard Covers)
transfer flow auxiliary tank 40 gallon
40 Gallon: 48″L x 19″W x 20″H / short & long beds
40 Gallon Under Toolbox Aux Tank
Transfer Flow Under Toolbox Auxiliary Tank 40 gallon
40 gallon: 49″L x 27″W x 12″H / short & long beds

50 Gallon Aux Tank (Standard Covers)

Transfer Flow 50 Gallon Under Tonneau Cover Auxiliary Tank in truck bed from above

50 Gallon: 61″L x 18.5″W x 18″H / height includes fill neck / long beds

75 Gallon Aux Tank

Transfer Flow 75 Gallon Auxiliary Tank in truck bed

75 Gallon: 61″L x 20.5″W x 23″H / long beds

100 Gallon Aux Tank

Transfer Flow 100 Gallon Auxiliary Tank in truck bed

100 Gallon: 61″L x 27″W x 23″H / long beds

 

FEATURES

  • Recommended for drivers who require additional fuel capacity but require a small footprint to maximize available bed space for 5th wheel hitches, Rambox beds, and cargo.
  • Won’t interfere with standard 5th wheel hitch.
  • Robot-welded seams provide extraordinary strength, unlike rotationally molded plastic tanks or cheaper steel brands.
  • Fuel tank systems include all components needed for installation.
  • TRAX 4™ computer-controlled automatic fuel transfers for worry-free operation with exclusive AutoTrans® technology.
  • Built from ReliaSteel®, high-yield U.S. aluminized steel powder coated black for superior durability and strength.
  • Baffled to prevent fuel sloshing.
  • 6 year, unlimited mile warranty.
  • Made in the USA.

Other Auxiliary Tank Options:

  • Transfer Flow Auxiliary Fuel Tank
  • All Auxiliary Tank options

Additional information

Size

100 Gallon, 37 Gallon Under Canister Tonneau, 40 Gallon Under Tonneau, 40 Gallon Under Toolbox, 50 Gallon Under Tonneau, 75 Gallon

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Frequently Asked Questions

Yes. The Transfer Flow in-bed auxiliary tank is designed to be compatible with RamBox-equipped trucks and trucks with factory-installed 5th wheel prep packages or other 5th wheel hitches. That said, bed length and tonneau type determine which of the six configurations you need. Contact us with your truck details and we'll confirm the correct fitment before you order — that's what the free pre-offer spec review is for.
The TRAX 4™ operating system with AutoTrans® technology monitors your factory fuel level and automatically transfers fuel from the auxiliary tank as needed. There are no driver-activated switches or manual transfer steps required. The system maintains your factory tank at an optimal level, which means you refuel less often and don't have to think about the transfer process while operating the vehicle.
Lead times vary by configuration and current factory production schedule. We arrange LTL freight nationwide and ship free to your location. If you have a specific deadline — seasonal fleet deployment, a job site startup, or a route change — contact us before ordering and we'll confirm the earliest possible ship date. We don't overpromise lead times. If we can't hit your window, we'll tell you upfront.
Yes. Tank Vault is an authorized dealer for Transfer Flow. Every auxiliary tank we sell ships as a complete, factory-built system with Transfer Flow's warranty coverage intact. We don't sell refurbished, modified, or third-party replica tanks. What arrives at your door is the same heavy-gauge steel system that Transfer Flow builds at their facility — complete with the TRAX 4™ operating system, preassembled components, and full manufacturer documentation.
That's exactly why we offer a free pre-offer spec review. Tell us your truck model, bed length, tonneau type, and any hitch or toolbox configurations before you order. We verify the correct tank size and fitment against Transfer Flow's application data. If a tank arrives and doesn't fit because we missed something on our end, we resolve it — 30-day return window, uninstalled and in original packaging.
Yes. Every Transfer Flow auxiliary tank order ships with the manufacturer's installation instructions, warranty documentation, and TRAX 4™ system operating guide. The sending unit, rollover valve, and fuel filter arrive preassembled in the recessed cover box, so installation is straightforward. If your operation requires additional documentation for internal procurement or fleet records, contact us and we'll work with Transfer Flow to provide what you need.
SKU: 0800116180 Categories: , Brand:

The Tank Vault Promise

Pay as low as $56/month with Affirm. Every Transfer Flow auxiliary tank ships with the Tank Vault guarantee behind it.

Free Shipping LTL freight delivery to your job site or fleet yard — ships free, no minimums.
30-Day Returns Uninstalled, original packaging — if it doesn't meet your spec sheet or arrives damaged, we resolve it immediately.
Free Pre-offer Spec Review We verify your truck configuration, bed length, and cover type before you order. Wrong fit caught before it ships.

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About transfer flow Auxiliary Tank

transfer flow is a trusted manufacturer of premium auxiliary tank. TankVault is an authorized dealer offering the full transfer flow lineup with free delivery, price match guarantee, and expert support.

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