GM HD 56-Gallon Fuel Tank Upgrade

Updated Feb 19, 2014

Transfer Flow GM HD fuel tank


Installing a 56-gallon Transfer Flow fuel tank replacement and F.A.S.S. filter system on 1 2008 GMC Dually 4Ă—4

By Bruce W. Smith

Fuel. It dictates how far we go and when we need to stop.

On many days it seems there’s plenty to get the job done, and on others, when time is pressing, the fuel gauge seems to fall way too quickly.

The aggravation of having to watch the fuel needle magnifies itself when our pickups are towing a big trailer or the bed is loaded down with tools and equipment.

Let’s face it: Today’s factory fuel tanks are just too small for those who work their trucks long and hard.

Our Mobil Delvac-sponosred 2008 GMC Sierra Crew Cab 4Ă—4 Dually is a prime example of a work truck in need of a bigger fuel tank.

The Duramax puts a hurt on the 34-gallon factory tank when rolling its 9,000-pound bulk down the road. Put a 5-ton equipment trailer on and fuel economy drops from 11mpg to around 8mpg, or a driving range of about 240 miles.

Such a driving range is neither convenient nor acceptable for some diesel pickup owners.

A ready solution is to swap out the plastic OE fuel tank for a higher capacity, steel replacement. (See how-to gallery.)

The 56-gallon one we slid under Mobil Delvac’s Big Red is a new offering from Transfer Flow, a long-time builder of premium aftermarket fuel tanks.

Transfer Flow’s OE steel replacement tank is baffled, powder-coated for durability, carries a three-year/60,000-mile warranty, and comes with all the hardware for a clean, factory-look installation.

It also meets all federal and state emissions regulations, so it’s a legal fuel tank.

Upgrading to a bigger fuel tank is also the perfect time to upgrade the fuel flow and filter system because some of the same labor is required for both installations.

For that we turned to FASS Fuel Systems.

The FASS filter system removes all types of fuel contaminates including emulsified water, air/vapor, and debris. Much more so than OE water/fuel filters.

FASS Fuel Systems Titanium Series filter/pump kit carries a lifetime warranty, improves mpg and cold-weather starting.

The Titanium Series kit we installed also takes a load of the OE fuel pump by using a heavy duty lift pump that has a flow rate of 95gph for the version used on our 2008 Duramax.

FASS claims that’s why their fuel air separation system (aka F.A.S.S.) improves fuel economy by up to 11 percent in diesel pickups pulling heavy loads and gains of 2-3mpg running empty.

They also say injector life is increased while lowering maintenance costs over the long run.

Truck Supply and Outfitters (, near our offices in Tuscaloosa, AL, swapped in the Transfer Flow fuel tank and installed the FASS filter system in our Mobil Delvac Dually in about a half-day.

Now Big Red is ready for the long run – both literally and figuratively. – Pro



Transfer Flow:; 800-442-0056

FASS Fuel Systems:; 866-769-3747

Truck Supply and Outfitters:; 205-553-4203