GMC Motorhome

The GMC motorhome was produced by the GMC Truck & Coach Division of General Motors for the 1973 through 1978 model years in Pontiac, Michigan, USA. It was the only complete motorhome built by a major auto/truck manufacturer producing what GMC hoped would be their halo vehicle. Part of the reason this vehicle is so different from other motor homes of the era is that it was not conceived as just a "camper," but as a vehicle for comfortable travel as well. The design was radical for the day with front-wheel drive and a low profile, fully integrated body. At the time (as now), motorhomes were built by recreational vehicle manufacturers on bare frames and drivetrains supplied by a chassis manufacturer. GMC built the bodies and in most cases the interiors in-house, and designed the chassis and drivetrain to create a motorhome enclosure that could be adapted to a range of purposes. Empty shells were supplied to other RV manufacturers for upfitting the interiors and also to specialty manufacturers for a range of custom purposes ranging from mail delivery and mobile training facilities to people movers and ambulances. It was built in 23-and-26-foot (7.0 and 7.9 m) lengths.

The motorhome had a front-wheel-drive transaxle used in the Oldsmobile Toronado and Cadillac Eldorado with an Oldsmobile 455 cu in (7.5 l) V8 from the Toronado, but the later models made use of the 403 cu in (6.6 l) V8. Both used the GM-designated Turbo-Hydramatic 425 automatic transmission, with a wide chain drive to connect the output of the longitudinally oriented engine to the transmission. The final drive was connected directly to the transmission, and power was fed to the front wheels using half-shafts that ran under the front portion of the engine. The engine was fueled with regular gasoline stored in two 25-US-gallon (95 l) tanks.

The GMC was equipped with front disc brakes and drums on all four rear wheels. A popular owner modification puts disc brakes on a pair, or sometimes all four rear wheels as well. The front-drive configuration eliminated the driveshaft and rear differential and solid axle found on most front-engined motorhomes. As a result, the floor could be designed only about 14 inches (36 cm) above the roadway. The low floor was too low for a rear cross axle, and GM designed the rear suspension as a tandem pair of wheels, mounted on bogies which rode on pins attached to the sides of the low-profile frame. With the exception of the wheel wells, the rear suspension does not intrude into the living space. The rear bogies are suspended using a double-ended convoluted air bag that is pressurized by an automatic leveling system to maintain the designed ride height. The leveling system can also be manually controlled to level the coach at a campsite. The overall chassis design, from the use of an existing GM E platform powertrain and a modified rear suspension has been considered an early ancestor of the crossover.

The motorhomes were built in either 23-foot (7.0 m) or 26-foot (7.9 m) length, with about 90% of the total production being the latter. The wheelbase from the front wheels to the centerline of the rear tandem pairs is 140 inches (360 cm) for the 23-foot (7.0 m) coach and 160 inches (410 cm) for the 26-foot (7.9 m) coach. All GMC motorhomes are 96 inches (240 cm) wide and about 9 feet (2.7 m) tall including the usually-installed roof air conditioner. Interior head room is 76 inches (190 cm).

Gross vehicle weight rating for the 23-foot (7.0 m) coach was 10,500 pounds (4,800 kg) and 12,500 pounds (5,700 kg) for the 26-foot (7.9 m) coach. Most GMCs with factory interiors have a 30 US gallons (110 l) freshwater tank and a 30 US gallons (110 l) holding tank.