The 1979 GMC Sierra Classic Is A Beast (10 Surprising Ways)

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“Start your trucking in a GMC pickup” is how the sales brochure described pickups in the 70s. What are ten surprising ways the GMC Sierra Classic is a beast?

The truth is that being a beast can be good or bad. While the 1979 GMC Sierra Classic was one of the most reliable trucks that GMC ever made, it was not without its share of struggles. As part of the third-generation C/K models, the “Square body” truck was widely recognized as a workhorse on the farm and the job, but it wasn’t the best-selling truck. Of course, it did what trucks do - it worked its tail off. But like a good 4x4 pickup, it had to overcome some rough terrain along the way.

The 1979 GMC Sierra was part of the third generation of C/K trucks to be produced by General Motors from 1973 - 1991. The truck known as the “square-body” was rugged but often doubled as a personal vehicle for many Americans. It was one of the first trucks to offer a dedicated diesel engine.

There are some surprising things to learn about the 1979 GMC Classic. The Classic was one of four trim levels offered; Sierra, Sierra Grande, High Sierra, and Sierra Classic. Considered the top trim level back in the late 70s, the Classic trim was offered in Wideside or Fenderside configurations and even had a few quirky design packages along the way. While Ford may have owned the market on half-ton truck sales, 1979 was still a good year as far as GM was concerned. Being an underdog can sometimes be an advantage to an automaker because it makes you work hard to differentiate yourself in a crowded field. That happened in the late 70s as GM attempted to chip away at a growing populace that continued to move away from larger trucks and care to smaller imports.

So, what made the 1979 GMC Classic so special that now collectors are scouring the nation to find them? Let’s explore ten surprising ways this truck made a name for itself.

Table of Contents


What was happening in the 1970s?

First, a bit of history. The third generation of C/K trucks began in 1973 and was a radical departure from the previous models. The round-line (but later dubbed “square-body” by owners)

was the first kind of truck to be tested in wind tunnels and, with extensive computer analysis to improve aerodynamics. The oil embargo of 1973 was fresh on the minds of everyone, and the government was aggressively pushing auto companies to figure out a way to improve mileage. Since trucks were so bad at guzzling fuel, they were an easy target, so the engineers at GM and other manufacturers got to work.

What are Ten Surprising Ways the 1979 GMC Classic is a Beast?

Here are our favorite things about the 1979 GMC Sierra Classic.

This Truck Provided Some Stability in an Ever Changing World

Even though smaller and smaller four-cylinder trucks were invading from overseas, There was still a need for a C/K class, half-ton truck, primarily in the agricultural and construction industries. GM didn’t change much when offering the 1979 model. The same engine choices were offered, including the available diesel that had been added just a year earlier.

The base MSRP for a 1979 GMC truck was $4895, which reflected about a 14% increase over the previous year. There were 120,430 units produced. (Ford pushed out over 400,000 F150s).

The Gas Powered Engine Choices MatoTruck a Beast

They were several engine choices for the 1979 Sierra 1500. The standard was the 4.1L In-line 6, but there were options - including a 5.0 V8, 5.7 V8, 7.4L V8, and a 5.7L V8 Diesel. The horsepower and torque specs are listed below -

Engine Horsepower Torque
4.1L 250 CID inline 6 100 horsepower at 3,600 rpm 175 lb/ft at 2,000 rpm.
5.0L 307 CID V8 115 horsepower at 3,600 rpm 205 lb/ft at 2,000 rpm
5.7L 350 CID V8 125 horsepower at 3,600 rpm 225 lb/ft at 1,800 rpm
6.6L 400 CID V8 185 horsepower at 3600 rpm 220 lb/ft at 2400 rpm
7.4L 454 CID V8 240 horsepower at 4,000 rpm 355 lb/ft at 2,800 rpm.
5.7 V8 Diesel 120 horsepower at 3600 rpm 220 lb/ft at 1600 rpm
5.7 L V8 17mpg - 22 mpg (19 com) 437 - 494 miles

There was an Option for a Diesel Engine

For some reason, GMC decided that it would be a good idea to offer potential owners the choice of gas engines or the 5.7L Diesel that they had been using in some of the passenger cars. Their thinking was that a diesel engine designed to help increase fuel economy could also increase torque for towing. In addition, because a diesel engine has fewer moving parts than a normal combustion engine, the engineers thought that they were also increasing the engine's lifespan. Serious truck owners needed to depend on their haulers since they were constantly putting their trucks through the grind of everyday use.

The only trouble was that the diesel engine was a disaster. GM offered the same diesel engine in many of their sedans, beginning with the downsized Olds Delta 88. There were numerous complaints concerning the engine in passenger vehicles (by this time, Buick, Chevrolet  Cadillac were all slapping the 5.7 diesel into their passenger vehicle lineups as an engine option). The problems centered around blown engines because the same number of engine bolts were being used (the motor simply could not handle the added pressure strain). The truth is that most hard-working Americans did not trust the diesel engine in a truck, and they avoided them like the plague. Eventually, GM would improve the 5.7 Diesel before completely abandoning it.

The 1979 model was the First for a Catalytic Converter

Up until 1978, truck owners could opt for an F44 (GMC called it a heavy half) that kicked the new emission standards in the mouth. There was a real tug of war between the government and automakers about installing the exhaust scrubbers on vehicles. The government eventually won the war, but the car companies came kicking and screaming. In 1978, GMC modified the frame to make room for the cat so as to comply with federal statures, which required all vehicles with a GVWR of 6,000 lbs or less to be so equipped. But GM offered a Big10/F44 designation that allowed owners (other than California) to bypass many of the EPA mandates. Unfortunately, the government decided to raise the basic requirements in 1979 so that the only truck that could bypass the requirements was the one-ton. From 1979, all 1500s, regardless of trim, were equipped with converters. This requirement ate into the sales because many truck owners didn’t like them, insisting that their trucks performed better without the added equipment. It was a hard sell to a Midwest corn farmer.

Double Walled Steel Panels Made this Truck Tough

There was a growing emphasis on vehicle safety in the 70s. With the NHTSA testing vehicles' ratings in crash tests and publishing the results, the government and the public began to realize how unsafe the vehicles they were driving were. (Some automakers were even installing airbags into vehicles). To help counter this and make the truck more rigid, back and door panels were reinforced with doubly welded panels to improve the integrity during a crash or side impact. Engineers were trying to make the C/K more of a tank on the roadway, which is what it already was.

You Could Get a Fenderside with Cool Looks

The 1979 GMC Sierra Classic came with two types of cargo beds. The first was called the “Wideside” and came with a ribbed-steel floor bed, making sliding materials in and out easy. It was a “double-wall” constructed full-width pickup box, with a secondary line running down the length of the truck toward new wraparound tail lamps.

The second type, Fenderside by GMC, was a pickup box featuring steps and exposed flanged-out fenders. Initially, only wood floors were available, allowing owners to nail stuff down. (There were holes in the sides for effective tie downs, but somehow the engineers got the idea that owners like hammer nail holes in the wooden beds). Eventually, the ribbed steel bed was offered. The Fenderside gave the truck a more squatty appearance, a bulldog look. And while it wasn’t the first truck to offer a side step, it was a great option for workers who needed to dig around in the tool boxes they put into the bed of their trucks.

The Interior Options were Upgraded on the Classic

Realizing that more and more people were using their trucks to haul families around, GMC offered the standard 6.5-inch foam bench seat as a part of the 1979 GMC Sierra. In the Crewcab, you could seat six people. The interior room was a hefty 42.2 legroom and 40.5 inches of headroom. Other options on the Classic included power windows, power locks, six position tilt steering wheel, upgraded AM/FM radio with eight-track as an option, a full instrumentation panel that included voltmeter, oil pressure and engine temp gauge, carpet lower door panels, storage pockets and leather door closing assist straps. There was even an option for vinyl seating surfaces and bucket seats with a center console.

The Truck had Full-Time Four-Wheel Drive

The truck came with a four-wheel drive system that operated all the time when customers opted for the automatic transmission. The system compensated for variations in speed, whether off the road or on the highway. It was also possible to lock the axle and bypass the differential by shifting a lever inside the cab to the “High loc” or “Low loc” position. Gone were the days of getting out of the truck and manually locking or unlocking the freewheeling front hubs. You didn’t even need to shift into four-wheel drive. The system was one of the first of its kind, paving the way for many AWD systems in use today.

There were some Awesome Appearance Packages

If you wanted your truck to stand out, there was an Amarillo Appearance Package that could be ordered for an additional $450 - $1000 depending on which of the three offerings was selected. The Amarillo package was a light cream or corn-colored paint job with bright yellow, orange, and red stripes down the lower side that ran the length of the truck. The Amarillo GT was a bit of an upgrade, and the Amarillo Cowboy Cadillac offered a plush interior.

Another appearance package was very limited and is considered one of the rarest Classics (it is so rare that no one has found one). The Mule Package was a limited offer from the 19 area Chicago dealers offered. It included wooden rails sticking up from the bed, had a mule emblem on the back, body side molding, and spoke wheels. You could order the Mule Edition with any 1979 pickup, but it is unclear if many of them were sold.

The Truth is Finally Printed

In the mid-70s, GM found itself in a quandary. The popularity of the Olds 88 with a rocket V8 was outstanding. The only trouble is that GM was substituting a different engine made by Chevrolet. When owners found themselves driving cars that were not what they believed, the flood gates of litigation poured in. GMC faced a deluge of class-action lawsuits about interchanging parts and engines with other divisions, namely Chevrolet. The litigation settlement forced GM to start printing in their brochure a disclosure that admitted that General Motors did not build some components of their trucks. Their reasoning was that to meet overwhelming public demand, and sometimes substitutions had to be made. Even though most everyone knew this fact already, the courts insisted it had to be in black and white. The 1979 brochure has a complete section dedicated to this admission, and while it made little difference for sales of that year's model, it did begin to impact the ability of GM to operate profitably in years ahead, leading to the demise of Pontiac in 2010 and Oldsmobile in 2004.