#HISTORY/MOTORHOME: Evolution of the 1973-1978 GMC MotorHome

BY Mike Bumbeck—A longstanding tradition in the recreational-vehicle manufacturing world is to take an existing heavy or super-duty truck chassis and simply have a coachbuilder add the home on top. Not so for the GMC Motorhome built from 1973-1978.

The standard 26ft long GMC Motorhome chassis with single front axle and twin rear bogies mounted to the frame.

General Motors had other plans and with its introduction in 1973, smart engineering made the GMC MotorHome a user-friendly recreational vehicle for the Space Age.

While the underlying chassis and drivetrain technology of the modern recreational vehicle has been improved over that of, say, a 1972 Travco Dodge Mahal, what is born as a truck or bus chassis will always be a truck or a bus, no matter how fancy its clothes. The GMC MotorHome changed this approach for ever.

The Kohl’s discuss the ups-and-downs of GMC Motorhome ownership over four episodes.

With a growing American market and increasing demand for recreational vehicles in the late Sixties and into the Seventies, GMC set out to modernize the way what were known as motorhomes were built; applying the latest technology and forward thinking, GMC redefined the recreational vehicle in order to distance the platform from early 1900s truck chassis technology, moving recreational vehicles into the future. While the Seventies were certainly about wide, they were also about low. GMC’s new recreational vehicle, or RV, would have a low center of gravity for improved handling. A low roofline would prevent underpasses from peeling up the top like a can of sardines while motorists were out enjoying America’s scenic roads.

The next requirement was to have enough ground clearance to drive into any of America’s National Parks without issue. While a streamlined RV was not a new idea, what GMC engineers achieved under the skin is what sets the GMC MotorHome apart, even decades after its introduction.

With the design parameters settled, work commenced at the GM Tech Center in Warren, Michigan, on a space-age RV that would glide over the roads and into a 1970s-conceived future; it would be an entirely modern fiberglass and aluminum Conestoga wagon. If space was the new frontier beyond Earth, then a smooth ride and car-like handling was the new frontier of recreational vehicles. Models were made first in scale and then full size. The conventional RV-truck chassis model was scrubbed, and a new design was created from scratch.

Dealer sales video showing a 1973 pre-production unit at Milford, MI, GM Proving Grounds.

The powerplant of the GMC Motorhome certainly clashed with conventional motorhome propulsion layouts, but it was the key element in meeting the design requirements of what would become America’s most sophisticated recreational vehicle in 1973. Thinking out of the box, GMC dipped into the well of GM powertrain choices, and chose not a truck drivetrain, but rather one from a car: the Oldsmobile Toronado 455-cu.in., 265hp V-8, complete with its front-wheel-drive setup. Placing the engine and transmission in front of the motorhome meant not having to make space for big rear-drive truck driveshafts and bulky fixed rear axles that would usually run through the width of the coach.

A “Palm Beach” Model 260 GMC Motorhome with optional Ragusa ladder, Alcoa wheels, and painted fiberglass spare tire cover.

A complex and expensive hydro-pneumatic rear suspension was dropped for a less expensive but effective air bag system. The suspension graced the GMC Motorhome with an independent rear suspension on four rear wheels, which could be leveled from inside the cabin. A disc brake-equipped torsion bar arrangement up front joined the four drum units out back for six-wheel power braking.GMC designed a frame of heavy-gauge aluminum and skinned it with a combination of molded fiberglass and aluminum to form the body.

 Final Assembly at Plant #3 in Pontiac, MI 

Step up into a GMC MotorHome as you would into any other motorhome, but only once inside does the true genius of the design become apparent. Like many a split-level suburban house, the GMC MotorHome has a step-down, or sunken, living area.

Page from a Palm Beach product brochure showing the interior with cabinetry over galley-area only.

The absence of conventional truck underpinnings allowed for a low floor and accompanying low center of gravity, and the low roofline was achieved without loss of interior space. The GMC MotorHome looks almost compact compared to conventional truck-frame units, and many hold that the GMC MotorHome has the finest riding and handling of any recreational vehicle, even in modern times.

Final Assembly at Plant #3 in Pontiac, MI 

At the very base of the model spectrum for the 1973 model year was the TransMode. These unfinished “blank canvas” versions were sold to some coachbuilders for finishing, as well as to many companies for custom use. Mobile library branches, Eyemobiles, and the like are just a few of the hundreds of conversions of the versatile TransMode models.

For the RV buying public, however, GMC encapsulated all of the Seventies into each and every interior. Acres of avocado Formica and forests worth of genuine simulated wood went into the production and installation of the interiors at the Gemini plant in Mt. Clemens, Michigan. The 23-foot version of the RV was no less deluxe than the 26-footer: According to original sales materials, the short version came equipped with the same high-level furniture as its longer counterpart.

The first four editions of the GMC Motorhome were named after America’s National Parks. The Canyon Lands, Glacier, Painted Desert and Sequoia RVs were available in 15 different floor layouts and six different colors, which made for a near-endless array of personalization.

The first episode in an interview series produced my MKCREATIVEmedia for My Motorhome Life.

Production of the GMC Motorhome ceased in 1978 after nearly 13,000 units were built. Sadly, the unique vehicle was a victim of rising gasoline prices that sent RV demand plummeting nationwide. A corollary discontinuation of the Oldsmobile 455-cu.in. V-8 sealed the fate of this futuristic RV.

A deep dive into the history of the GMC MotorHome and the reasons for its cancellation.

Still, all is not lost. With the end of the line came the beginning of a dedicated fan base and growth of a community that continues to roll on, restore and maintain the remaining stock of these sleek, futuristic homes on wheels.

(Parts of this article were originally written by Mike Bumbeck and published on Hemmings.com. No copyright infringement intended.)