1973-87 Chevrolet/GMC Truck Vehicle History

1973-1987 Chevrolet Trucks: The Square Body Era

The Chevrolet trucks from the 1973 to 1989 era mark a significant period in American automotive history, known for introducing the third generation of Chevrolet's C/K line. This period is notable for the introduction of several innovative features, changes in design, and a strong focus on functionality, durability, and performance that catered to both personal and commercial truck users. Here's an overview of key highlights and developments in Chevrolet trucks during this period:

Square Body Design: This era introduced the iconic "Square Body" design with the 1973 model year, characterized by its boxy, angular lines. This design became a defining look for Chevrolet trucks throughout these years.

Model Range: The range included the C10, C20, C30 (two-wheel drive) and K10, K20, K30 (four-wheel drive), offering a wide variety of options for different needs, from light-duty personal use to heavier commercial applications.

Engines and Performance: Chevrolet offered a broad spectrum of engines, including efficient inline-sixes and powerful V8s, catering to diverse needs from daily driving to heavy hauling and towing.

• Inline-Six Engines: The base engine for many models was the reliable inline-six, with the 4.1L (250 cubic inches) being a common choice. It offered a balance between fuel efficiency and enough power for light-duty tasks.
• Small-Block V8 Engines: Chevrolet's small-block V8s were widely used and revered for their balance of power and efficiency. The 5.0L (305 cubic inches) and 5.7L (350 cubic inches) engines were among the most popular, serving as a staple in both personal and commercial vehicles.
• Big-Block V8 Engines: For those requiring more power, Chevrolet offered big-block V8 engines, such as the 6.6L (400 cubic inches) and the 7.4L (454 cubic inches). These engines were designed for heavy-duty applications, providing significant towing and hauling capabilities.
• Diesel Engines: Introduced in the late 1970s, diesel options like the 5.7L V8 diesel (introduced in 1978) and later the 6.2L V8 diesel provided better fuel economy and durability, appealing to commercial users and those with heavy towing needs.

Innovations: The period saw numerous technological advancements, such as improved suspension systems for better ride quality, the introduction of diesel engines in the late 1970s for greater efficiency, and the early adoption of computer controls for emissions in the 1980s.

1988-1989: A Period of Transition and Consistency

The GMT400 Introduction: While Chevrolet launched the fourth-generation C/K trucks with the GMT400 platform in 1988, this change initially applied to the ½ ton models. These trucks featured a more aerodynamic design and modernized features, marking a significant departure from the square body style.

Continuity for ¾ Ton and Larger Trucks: Notably, the ¾ ton and larger trucks (C20, C30, K20, K30) maintained the square body design through the 1989 model year. This decision allowed Chevrolet to offer continuity for commercial and heavy-duty users while gradually transitioning its lineup to the new generation.

The Importance of the Transition

This period is particularly interesting for Chevrolet truck enthusiasts and historians because it showcases a time when both old and new coexisted, reflecting Chevrolet's strategy to cater to a broad audience by maintaining the rugged, reliable square body design for its heavier-duty trucks while introducing more modern, fuel-efficient, and aerodynamically designed models for the lighter-duty segment.

The late 1980s thus represent a pivotal moment in Chevrolet truck history, with the enduring popularity of the square body models among collectors and enthusiasts today highlighting their lasting impact and appeal. The gradual transition to the GMT400 platform for all models by 1990 completed a significant chapter in Chevrolet's truck development, setting new standards for design, performance, and efficiency in the years that followed.

The GMC trucks from 1973 to 1987

The GMC trucks from 1973 to 1987, paralleling Chevrolet's C/K series in the same era, share many similarities but also feature distinct differences that set them apart. Both brands were under the General Motors umbrella, which meant they shared platforms, drivetrains, and many design elements. However, GMC trucks were often marketed toward a slightly different audience, emphasizing professional and commercial use, though they were also popular with consumers. Here’s a look at the key differences between GMC and Chevrolet trucks during the 1973-1987 period, commonly referred to as the "Square Body" era.

Professional Use: GMC trucks were often positioned more towards the professional, commercial, and heavy-duty markets. They were advertised as being more rugged and durable, appealing to those who needed vehicles for work purposes.

Trim and Model Names: While Chevrolet named their trucks with the C/K followed by a number indicating the weight class (e.g., C10, K10), GMC used the Sierra nameplate across several trim levels (e.g., Sierra, Sierra Grande, High Sierra), indicating luxury levels rather than focusing solely on the vehicle's capability.

Engine Availability: Both GMC and Chevrolet trucks offered a wide range of engines, including inline-six engines, small-block V8s, and big-block V8s. However, there were slight variations in the availability and tuning of these engines. For example, GMC occasionally offered engines that were not available in Chevrolet trucks, such as the 305 cu in V6 engine specific to GMC in the early years of this generation.

Transmission Options: GMC trucks sometimes had different transmission options or availability, including the heavy-duty versions of manual and automatic transmissions that catered to the brand's focus on commercial use.

Exterior Design: While the overall body shape was nearly identical between GMC and Chevrolet trucks, GMC models often featured different grille designs, badging, and trim options. The GMC grille design was generally more pronounced, with a distinct look that differentiated it from the Chevrolet models.

Interior Differences: Interiors were largely the same in terms of layout and design, but trim packages, upholstery options, and badging could vary between GMC and Chevrolet, with GMC trucks occasionally offering slightly more upscale or different interior options.

Heavy-Duty Models: Both brands offered heavy-duty models, but GMC's focus on the commercial market meant that their heavy-duty trucks, such as the 1-ton and larger models, might have had different configurations or options tailored to commercial applications. This includes differences in chassis setups, suspension components, and axles designed for higher payload and towing capacities.

Perception: While mechanically similar, the market perception of GMC trucks was that of a more premium or professional-grade vehicle compared to Chevrolet's more consumer-focused branding. This perception was cultivated through marketing strategies and the slight differences in product offerings.

Legacy: Both GMC and Chevrolet trucks from this era have a strong following today, with enthusiasts appreciating the subtle differences between the brands. The "Square Body" trucks are celebrated for their durability, classic design, and ease of customization and repair.

In summary, while GMC and Chevrolet trucks from 1973 to 1987 shared many core attributes, GMC's branding, specific model offerings, and slight variations in styling and options catered to a demographic looking for work-ready or slightly more upscale truck options. These differences underscore GMC's unique position within the General Motors family as the brand catering to both commercial users and those seeking a premium truck experience.