Adding a Larger Fuel Tank to a 2015-Plus Tundra

Adding a Larger Fuel Tank to a 2015-Plus Tundra

If you do a lot of driving or towing, you know how much of a pain it is making frequent stops to fuel up. This is especially true if you have a Toyota Tundra, like our test subject for this article. Our ’15 Toyota Tundra 4WD Crewmax TRD Pro came stock with a 26-gallon gas tank. Yep, you read that right, 26 gallons for a full-size truck.

To give you a reference point, we drove this truck from North Carolina to Texas towing a rather large enclosed car trailer that was loaded. We stopped for gas about ever hour and a half. What was usually a 16-hour trip each way became especially aggravating with all of the extra stops. Granted the truck has a 7-inch lift and 37-inch tires, which got us a whopping 7.5 mpg, so that didn’t help either. But even the stock Tundras don’t get much better gas mileage while towing.

After this trip, we knew we had to contact Transfer Flow and order one of its 46-gallon direct-replacement tanks (P/N 0800114225, $1,299 MSRP) before we took any more road trips. This fuel tank is installed in place of the factory tank, only hangs about an inch lower than stock, and doesn’t require any modifications. It uses all of the factory mounting points and fuel pump while retaining the stock gauge readings. Once it arrived, we scheduled the help of a couple of friends and set a date to install it.

Because the truck is lifted, we didn’t even need to jack it up to access the tank. We used a couple of floor jacks with some blocks of wood and hand tools in a home garage. Even though we BS’d quite a bit, just like every group of friends when they get together to turn wrenches, it still only took about three and half hours to swap tanks and get the truck running. If you can use a ratchet and a screwdriver and have a few extra sets of hands, you can easily manage this upgrade yourself.

Transfer Flow builds its replacement tanks to be very user friendly. Since the new tank has been installed we’ve made another long-distance trip hauling a car trailer. This time we managed to go as long as four hours between fuel stops, which was well worth the time and money it took to install the new tank. Check out the next few pages to see how simple it was to install the tank. ST

The stock tank (our model had the TRD Pro skid plate) is easy to access.
Unplug the fuel pump control module on the driver’s side frame rail towards the rear tire and let the truck run until it shuts off.
Disconnect the OEM fill hose from the tank with a 10mm socket.
Disconnect the vent line from the canister and unplug the wire harness from the top of the tank near the rear.
Disconnect the fuel line from the front of the tank. If the truck is a Flex-Fuel vehicle, leave the line with the orange clip. Remove both lines on non-Flex-Fuel trucks.
Support the stock gas tank with a couple of floor jacks and remove the pins on the tank straps on the driveshaft side.
Remove the bolts on the tank straps from the frame side, then lower the tank about 6 inches towards the driveshaft. This will allow access to the top of the sending unit so that you can disconnect the electrical connector from the top. Keep all factory hardware because you will reuse it to install the new tank.
Now that everything is unhooked, lower the stock tank and move it out of the way, making sure not to spill any gas.
Here is the new 46-gallon tank (top) compared with the OEM 26-gallon tank (bottom). The new tank also comes with all of the hardware that you need to install it.
Install the front and rear strap extensions using the OEM clevis pin and stock cotter pins.
Using a large flat-head screw driver and mallet, unscrew the mason jar cap securing the sending unit to the OEM tank. Slide the cap over the fuel lines and discard. Remove the sending unit from the OEM tank making sure the gasket stays with the tank because it won’t be reused.
Make sure the new green O-ring that came with the Transfer Flow tank is in place. Orient the sending unit so its location tab is aligned with the smaller location slot in the new sending unit ring. The float should be facing the rear of the tank.
Place the Transfer Flow compression ring over the studs and secure it to the tank with the six flange nuts.
Install the roll-over valve into the tank. While pushing down, turn the valve clockwise to lock it in place.
Install the two 10-inch-long pieces of adhesive foam to the cross members where the tank straps will connect; this will keep the tank from rubbing.
Install the emissions tube and vent tube onto the tank to prepare it for installation.
Note where the fuel line connections are; this will make connecting them easier once the tank is in place due to the limited space and zero visibility.
With some floor jacks and the help of a couple of friends, slowly lift the new tank into place.
Once the tank is almost in place, connect the fuel lines to the sending unit, making sure the yellow plastic clips are securely in place.
Connect the new tank straps to the frame using the OEM hardware.
Connect the inner mounts of the tank straps to the extensions you added in step 10.
Once everything is in place, tighten the tank straps completely and reinstall the fill hose, vent tube and all of the electrical connections you disconnected to remove the OEM tank. Make sure that everything is fully connected to prevent any problems from occurring down the road


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