Six Decades Ago, General Motors Tried To Make Utility Trucks More Efficient By Making The Truck Bend In The Middle

Consumer trucks and military trucks tend to follow different development paths. The military wants its trucks to carry heavy loads and be highly mobile, while a consumer wants their truck to make their lives easier, and maybe look good doing so, too. What would happen if you combined both ideas into one truck? This is the Articulated General-Purpose Logistical Truck, or AGL-4, from General Motors Defense Research Laboratories. Back in the 1960s, this experimental pickup truck of the future, which was based on the Corvair 95, turned tighter, climbed better, and cleared more obstacles than a standard pickup truck. It did so using a genius articulating system that split the cab from the bed.

General Motors has supported military efforts for longer than a century. During World War I, over 90 percent of GM’s truck production was repurposed to support the U.S. Army. General Motors would then send more than 13,000 Model 16 trucks, 2,300 staff cars, 1,100 artillery tractor V8 engines, and many more additional vehicles into the frontlines. GM Fisher Body built 1,600 De Havilland DH-4s while Buick and Cadillac built more than Liberty aircraft engines. GM also sent mortar shells into the war.

In World War II, General Motors sent a mind-boggling amount of equipment overseas, including more than 850,000 trucks between GMC and Chevrolet alone. Then there were the over 21,000 GMC DUKWs. The General also built tens of thousands of North American Aviation P-51 Mustangs, North American B-25 Mitchells, North American T-6 Texans, Grumman F4F Wildcats, and Grumman TBF Avengers. GM’s Opel subsidiary also supplied trucks to Germany’s armed forces.

GM would continue to grow its defense arm through the Korean War and the opening of the Vietnam War. By 1959, General Motors started to get experimental with its defense department. Instead of just supplying the military with equipment, General Motors wanted to be at the forefront of military equipment development. One of the lesser-known projects to come out of this effort was the Articulated General-Purpose Logistical Truck, which tried to be a commercial truck and a military truck at the same time.

The “Agile” Truck

The Articulated General-Purpose Logistical Truck, codename AGL-4 and said like “Agile,” was a product of 1965. Sadly, despite my best efforts, I could not find any documentation from GM itself about this project online. Instead, I’ve found only footage that explains what GM’s teams built. Embedded below is a high-definition remastered video showing the beauty of the AGL-4. Sadly, due to image rights restrictions, I could not share screenshots from it. Click here if you cannot see the video:

While the AGL-4 had the bones of a Corvair 95 pickup truck, it wasn’t an effort by Chevrolet. Instead, it was technically a defense project by GM Defense Research Laboratories. GM offers more information about this division:

GM continued to grow its defense business, expanding its research and development footprint throughout the late 1950s and 1960s. GM Defense Systems Division, later re-named GM Defense Research Laboratories, formed in November 1959 to increase support for the national defense effort. GM purchased a facility near Santa Barbara, California in August of 1960 where work began on military projects such as the purpose-built GMC Minuteman I Missile Transporter Erector Loader and amphibious Sidewinder prototype.

However, the greatest contribution of this group was in the Space Race with innovations such as GM’s inertial guidance and navigation system, which helped enabled NASA’s first successful crewed lunar landing during Apollo 11 mission on July 20, 1969. GM also pioneered lunar mobility by developing the electric drive system, mesh wire wheels, suspension, drive controls and other mobility elements for the first Lunar Roving Vehicle that drove on the Moon as part of Apollo 15 in 1971 followed by Apollo 16 and 17 missions as well.

GM returned to its roots in military mobility in the early 1980s, winning the U.S. Army’s Commercial Utility Cargo Vehicle (CUCV) business, GM’s first significant light-truck military offering since WWII. General Motors Defense Group was formed in the early 1990s, coordinating work with many GM divisions, including Hughes Aircraft, Electro-Motive and Detroit Diesel Allison in their efforts to support every branch of the U.S. military on land, in the air and at sea. Dubbed “The Ultimate Ally,” General Motors Defense Group facilitated procurement of GM’s commercially proven gas, diesel and turbine powertrain technology in almost every type of ground and seafaring military vehicle.

Here is a longer, more detailed video on the AGL-4. Click here if you do not see the embed below:

GM’s video on the truck wastes no time in explaining what the company’s engineers cooked up. The narrator states that the AGL-4 was built to evaluate a concept for a low-cost, high-mobility truck that bridges the gap between commercial and military trucks. This would be one truck for commercial deliveries, construction companies, recreation, ranching, farming, or military use.

The AGL-4 was 15 feet long, sported 44-inch tires, and could carry a 1-1/4-ton payload. The brilliance of the AGL-4 was its running gear and articulated design. The front of the truck is a Corvair 95 pickup truck, which was already an unconventional piece of kit.

Innovative Bones

When Chevrolet launched the Corvair in 1959 for the 1960 model year, GM had shown America that it had done something innovative. The Corvair had an air-cooled flat engine placed in the rear, unitized construction, an independent suspension, a transaxle, low-profile tires, and more.

The Corvair would also prove itself to be a durable vehicle, too. Two Chevy Corvairs allegedly crossed the Darién Gap, the roughly 60-miles of road-free mountainous jungle, swamp, and rivers that separate Panama and Colombia. The Corvairs’ support vehicles, 4×4 Suburbans, apparently weren’t able to achieve the same feat.

The Corvair’s platform also allowed for an amazing variety of vehicles, as I wrote:

And the Corvair wasn’t just limited to a durable sedan, wagon, and coupe. General Motors made utilitarian variations of its Corvair. These included forward-control vans and quirky pickup trucks. For a short period of 1961 and 1962, you could get a Corvair 95 Loadside pickup. These were forward-control pickups with a typical rear gate. But the cooler version, sold between 1961 and 1964, was the Corvair 95 Rampside pickup. The Rampside maintained the rear gate, but also added a ramp to the side of the bed (see center photo below). This allowed for the easy loading of motorcycles, lawn equipment, or anything else that you don’t want to lift into the bed of a pickup.

The folks of the Corvanatics Corvair enthusiast site note that the ramp had the same double-wall construction of the bed’s walls, and it could handle 1,000 pounds of whatever you wanted to roll up it. And with a gross vehicle weight rating of 4,700 pounds, they could carry a 1,900-pound payload.

The beds were a bit strange, too, as a Corvair pickup’s was stepped thanks to the drivetrain in the rear. So they were a brilliant idea with a few kinks. And in case you’re wondering, 95 is a reference to the trucks’ 95-inch wheelbase, shorter than the 108-inch wheelbase of a regular Corvair, Hemmings notes.

In creating the AGL-4, GM Defense Research technically built a super Corvair 95. The Corvair’s air-cooled flat-six was relocated to a position under the cab. It’s unclear which Corvair flat-six is under there. If this truck started life as a Rampside, that could be a 145 cubic-inch engine with 80 HP on tap.

Anyway, GM says that the engine sends power through a two-speed Powerglide automatic, like it normally would, but then things get different. That power then reaches a two-speed transfer case and then a four-wheel-drive system. The most important part of this build is an articulating yaw and roll joint, which allows the bed and cab to twist and articulate freely and independently as the truck traverses rough terrain. Specifically, GM says that the truck has 35 degrees of articulation. Sadly, since I do not have access to any documents, I cannot show you a diagram of how this joint works or how it keeps power flowing to the rear differential.

What I can say is that GM engineered the cargo body to act as a sort of powered trailer. The joint can be disconnected, and a dolly can be temporarily connected so that the cab can drive away from the bed. Then, the cab could drive on its own over to another cargo box. This gave the AGL-4 some modularity as one cab could attach to different kinds of cargo boxes.

GM seemingly thought out the little things, either. The bottom of the cargo box holds a space-saver spare tire, which is eight inches shorter than the 44-inch off-road tires. If a mechanic needs to service the running gear, the cab tilts forward.

The AGL-4 Was Seemingly Unstoppable

After explaining how the rig worked, GM’s video shows the AGL-4 at work. The huge tires, which were kicked out to almost the corners of the truck, permit it to drive into and out of a five-foot ditch with ease.

The truck then climbs an 18-inch high stair without bottoming out. More impressive is the articulation section, where a driver rolled the truck over 12-inch-tall blocks. The joint between the cab and bed allows all four wheels to keep touching and thus, provide traction. GM says that having that joint means that the AGL-4 was able to have a lighter structural design compared to the beefy chassis a rigid truck would need to handle the same course. GM then shows the truck climbing a 60 percent grade.

Later in the video, a driver takes the truck on a rough off-roading trail that’s full of huge dips that would challenge the articulation of even the best Jeeps. But the AGL-4? All four wheels remained in contact all the way through.

Since the AGL-4 was designed for farming and military needs, the cargo box was built to fit 10 men. Add three more people in the cab, and the rig can transport 13 people to the field. The video then repeats the same off-roading test as earlier, but now fully-loaded with men. At 40 mph off-road, GM claimed, the men in the cargo bed were comfortable.

Another benefit, GM said, was that thanks to the articulation, the truck had a turning diameter of less than 38 feet, which GM’s standard trucks just couldn’t match. An AGL-4 could drive circles in the same space that a rigid truck would need to perform a three-point turn to drive in.

For an ultimate test, GM found a mud pit and sent a military Jeep, a GMC K-series with mud tires, and the AGL-4 into the pit. Only the AGL-4 powered through without stopping, even though it had less power than the average pickup truck of the day. Part of the magic, GM said, was that the AGL-4 was able to use its articulation system to waddle like a duck through the mud.

Finally, GM then sent a Chevrolet 4×4 pickup truck into some sand dunes with the AGL-4 giving chase. Once again, the standard truck got stuck. But, since the AGL-4 had floatation tires, GM noted, it floated right over where the Chevy got stuck. When the AGL-4 did get stuck, the driver was able to free it by making the truck duck waddle again.

What Happened To The AGL-4?

Sadly, it’s not known what happened with the AGL-4 project or with the truck itself. Obviously, it did not go into production. But there’s no explanation as to why it failed. If I had to hazard a guess, I would bet that the articulation mechanism was an expensive bit of kit.

At the same time, perhaps the need for the military to have such a vehicle faded. In 1961, the Advanced Research Projects Agency launched Project Agile. The project called for research to support U.S. military counterinsurgency efforts in Southeast Asia. Project Agile ran through 1974 and covered a broad range of military prospects, from DARPA:

Along the way, subprojects included weapons (among them flamethrowers and what became known as the M-16 assault rifle), rations, mobility and logistics in remote areas, communications, surveillance and target acquisition, defoliation, and psychological warfare.

One of the developments was the “Truck, Utility, High Mobility, Light Duty XM561.” Inventor Roger Gamaunt had been developing an articulating six-wheel utility truck since 1947. In 1959, Gamaunt approached Ling-Temco-Vought (LTV Aerospace) with his truck idea, and in 1960, the conglomerate built the first prototype. Chance Vought was one of 50 companies that submitted proposals to build the XM561, including General Motors. Chance Vought won the contract with its M561 Gama Goat, which would be built by Consolidated Diesel Electric Company.

Was GM’s AGL-4 inspired by the Gama Goat design or by its predecessor? I cannot say. However, General Motors was certainly far from the only company dreaming up articulated trucks in the 1960s. Even Canadair Ltd., a company more known for its aircraft, cooked up an articulating truck.

While the AGL-4 did not go into production, it’s still a great piece of General Motors engineering history. GM’s engineering past is frankly incredible. This is a company that has built everything from a coal-burning turbine passenger car and a go-anywhere articulating truck to buses and locomotives that dominated their markets in America for several decades. It seems like the General Motors of the 20th century was capable of building anything.

If you happen to know more about the AGL-4 story, please send me an email at mercedes@theautopian.com. I would love to finish this story and fill in the gaps. Likewise, if you know some other examples of engineering history that should be known, I’d love to know!

Top graphic images: 1unsafe1/YouTube