- 1956 incorporated a year of work that made significant changes to the GMC truck brand, owned by General Motors. Looking for an increase in market share, GMC added more strength to the engine, redesigned the axles and transmission, and added a 12-volt electrical system for better lighting to attract customers. Yet years later, the most noticeable features on the GMC '56 are the unique front tube grille and short box truck bed that came with the vehicle.
- The stock engine pumped out six cylinders' worth of power, providing dependable performance and reliability that was expected of GMC trucks by returning customers.
1956 GMC 100 and 300 series pickup trucks weighed in at a 1/2-ton. The engine in both truck models measured approximately 270 cubic inches and put out between 120 and 130 horsepower, depending on the rpms at the time.
A more powerful eight-cylinder engine was also produced for the same time in 1956, producing up to 180 horsepower. The size on this engine reached as much as 288 cubic inches.
The 550 and 600 series trucks moved with an even stronger eight-cylinder engine that pushed out 210 horsepower and had up to 324 cubic inches in displacement. - The transmission for GMC trucks in 1956 used a three-speed design. The truck was slowed down by power brakes, a new approach in truck braking systems, which previously just used plain cable pulley systems for activating drum brakes.
The driveline was redone as well. The previous year's model had a torque tube driveline. The 1956 trucks began the use of GMC's open-driveshaft. This new design made it a lot easier for mechanics to get into the system to perform repairs. - Suspension was refitted to address the strength and vibrations of the stronger 1956 GMC engines being outfitted in the truck line. Road Shock Damper (RSD) Suspension was created and installed on the trucks with the hope of making the ride more similar to a passenger car than a cargo truck.
Additional accessory changes on the '56 truck included turn signals, enhanced rear mirrors on the truck doors, electrical windshield wipers and better lighting due to a new, brighter 12-volt electrical system.
In the wheel world, GMC took a new turn and began incorporating tubeless tires on its trucks for the first time in 1956. However, some customers still preferred inner tubes, so an option for tubed tires was still kept available through dealers.