Crackerbox Cabovers

• Cabover trucks were developed in response to laws that limited the overall length of trucks on the highway. By moving the cab forward and over the engine, the truck could be made several feet shorter, and the saved length could be added to the trailer instead, thereby increasing cargo space. The 1960 GMC cabover offerings included the aluminum-cab "F" series and the steel-cab "L" series. Although the aluminum-cab "F" models would be replaced by the Astro in 1969, the steel-cab models would continue production until 1981.
  
  

First Astros

• The Astro offered many improvements over the "Crackerbox" trucks. A larger cab provided more interior space and greater comfort for the driver, and larger windows allowed for better driver visibility. Upgrades to the truck's suspension improved its handling and ride, as well. The Detroit Diesel engines that were available in the "F" and "L" series of trucks were joined by optional Cummins diesel engines in the Astro line, and the Astro was available with a wider range of engine and drivetrain combinations than the "Crackerbox" trucks had been.
  
  

Later Improvements

• In 1971, GMC introduced the Astro-Aire rear suspension, a heavy duty air suspension system that provided resistance comparable to that of steel spring suspension systems. The Astro-Aire system was 1,000 pounds lighter than the spring system previously used on its heavy duty trucks, and the weight savings made the air suspension system an attractive option. In 1983, GMC addressed the problem of the cabover's relatively poor aerodynamic performance compared to conventional-cab designs with its Aero Astro package. The package included an air deflector on the cab roof that directed air flow over the top of the trailer, as well as side panels that covered much of the gap between the cab and trailer. The resulting reduction in drag increased fuel efficiency.
  
  

End of Production

• In 1981, GMC ceased production of its "L" series of steel-cab heavy duty trucks, ending 20 years of continuous production of the model and beginning the end of GMC's entire heavy duty truck line. The Astro and General lines would be discontinued six years later, and the Brigadier production line at Pontiac would be halted in 1988, marking the first time since 1911 that GMC produced no heavy duty trucks.