Classic Advisory: Blazer

Hot on the heels of International Harvester, Ford and Jeep, General Motors moved to introduce the K5 Blazer in 1969. Originally conceived as a short wheelbase competitor to the Bronco, Scout and Jeep CJ, who were much smaller, GM changed the game when it chose to base the Blazer off of the existing GM pickup line, and shorten it. This increased interior space, lowered the cost of production and development and offered several powertrain options from the get-go.

The Blazer quickly became popular as it married the off-road capabilities of a small truck with the luxury features like air conditioning and automatic transmissions that were widely available on full-size pickup trucks. By 1970, the Blazer was outselling International and Ford 2 to 1. International Harvester responded with the full-size Scout II, and Ford with the full-size Bronco.

Four-wheel-drive versions of the Blazer came with a solid front axle and leaf springs front and rear, while the two-wheel drive versions used an independent front suspension with rear trailing arms and coil springs. Both drive-line versions used drum brakes in all four corners until 1971, when the entire GM truck line got standard front disks. Luxuries, such as a tachometer, were optional.

Powertrain options consisted of the 250 and 292 inline-six engines and the 307 and 350 V8 engines. Power was fed through a three-speed Turbo Hydromatic TH350 automatic transmission or a four-speed Syncromesh SM465 manual transmission. Two transfer case options were available: the Dana 20 or the New Process NP-205. The Blazer had 8 inches of ground clearance and an approach angle of 35 degrees. The first generation Blazer totaled nearly 70,000 units in its first four years.

In 1973, GM’s line of full-size trucks was redesigned and updated, the Blazer fell into the mix as well. The trucks received full updates inside and out, and their powertrains were updated. Available power plant options were the 250 and 292 inline-six, the 305, 307, 350, and 400 V8s and the 6.2L Detroit diesel. Drivelines were NP-205 and NP-203 transfer cases and the vehicles featured Dana 44 front axles and Corporate 10 bolt rear axles. In the early 1980s, the 10 bolt was phased out and replaced with a stronger 12 bolt axle.

In the wake of the 1973 Oil Embargo, GM made the smaller displacement 305s with a 9.2:1 compression ratio. These engines produced nearly as much torque as the 350 giving a similar driving feel. However, these power plants were considered underpowered and prone to pre-detonation knocking due to heat soak in the heads.

In 1987, the GMT400 platform was released for the GM full-size trucks. The K5 Blazer, Suburban and crew cab trucks retained the previous platform until 1991. The GMT400 platform entirely revised the design with a new boxed steel frame and independent front suspension. This transition to the independent front suspension is largely considered to be the downfall of GM light trucks for the off-road segment.

Nineteen ninety-four spelled the end of the Blazer and was subsequently replaced by the larger Chevy Tahoe and GMC Yukon. Currently due to the revitalization of the small HD truck market by the wildly successful four-door Jeep Wrangler and Ford’s re-entry to the market with the new Ranger and yet-to-be-released Bronco, General Motors is expected to revive the Blazer namesake and enter the market again as well.

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