The chassis that GM introduced in 1960 revolutionized light trucks. With a double-arm independent front suspension and a trailing-arm rear suspended on coils (standard on Chevrolet, optional on GMC) it was more car–like than anything else on the market. That it took Ford five more years to introduce its own independent front suspension and Dodge didn’t have one until 1972 suggests that it was ahead of its time. And even then, those still employed leaf springs out back, just as they’d done from the infancy of the light truck.
The GM truck chassis lends itself very well to modification. With coils, spindles, and a C-notch (and a flip kit for Jimmies and leaf-optioned Chevys), a GM pickup can sit low enough to violate scrubline with all but the shortest-sidewall tires. Even with the disc brakes that came standard on the later pickups, they can stop respectably, too. And with good dampers and antiroll bars, a GM pickup can handle well enough.
But sometimes well enough just isn’t good enough. If nothing else, the latest generation of aftermarket chassis and suspension systems for passenger cars has utterly spoiled us. Art Morrison Enterprises (AME)—which basically created the sports chassis market segment nearly 20 years ago—proved to us that pretty much anything could match—if not surpass—the performance of modern sports cars. These chassis are such an improvement that people go to the hassle of grafting them into cars that never even had separate chassis in the first place. So, in light of that, it was only a matter of time until AME created a chassis for pickups.
That time is right now.
The AME crew fielded more and more requests for 1967-1972 pickup chassis as the light-truck market gained steam. While it prides itself in its ability to make a chassis for anything, the team didn’t feel all that comfortable just adapting its existing designs to the C-series format, at least for production. “These trucks are different for more than just their shape,” Vice President and Operations Manager Craig Morrison explains. “They’re wider and longer and in some cases people actually use them to haul things. That’s a lot to ask of components designed for use in a passenger car that may not even have a back seat.”
“It’s a clean-sheet design,” Matt Jones, chief engineer, adds. Among other things, they designed it around C-series knuckles, opening the door to brakes designed for those applications—brakes that you may already have. “We also had to make everything a lot stronger.” He points to the oversized front control arms, bushings, and rear links. “We debated whether or not to make those rear bars even bigger.” He admits that the latter was purely for perception. “When people think about trucks, they want to see big parts. We want them to feel comfortable that it’s overbuilt. But we’ve done the engineering on this—there’s no way anyone could bend much less break those links the way they are.”
It was really the frame itself that presented the greatest challenge. “With the wheelbase the way it is, trucks need a 6-inch-high framerail,” Craig notes. “But with a frame made 6 inches high the whole length of the truck isn’t smart.” Among other things it gets in the way of other components, pushes the bed floor up too high, and adds a bunch of unnecessary weight. The objective was to taper the frame down to 4 inches high for the ends, no simple task given that AME builds its frames from tubing.
To bring the two dimensions together, the crew cuts the larger tube down by a geometrically clever (and secret) way that maintains its walls and corner radii. The 2×4 end stubs slide into the tapered 2×6 side rails, the double-wall structure making those areas stronger. “That’s important because that transition is typically the weakest part of a frame,” Jones says.
The chassis come as pictured in the lead. The assemblies include a frame stepped to achieve full suspension travel without resorting to C-notching (which impairs structural integrity, you should know). Bolted to that frame are truck-specific control arms that mount forged Wilwood knuckles, a Detroit Speed rack-and-pinion unit, a Ford 9-inch–style axle housing, and the triangulated links required to connect that housing to the chassis. Jones went far out of his way to design the various subassemblies (like the upper-arm brackets and cab mounts) with as great a cross section and with as much surface-contact area as possible. The crossmembers accommodate common drivetrains (first- through fourth-gen small-blocks plus big-blocks and all transmissions) and shield under-vehicle components like the exhaust system. The driveshaft-loop crossmember accommodates exhaust pipes as large as 3 inches in diameter. And Jones took special care to give those pipes a clear shot over the axle and out the back. The chassis come set up standard for coilovers but the design accommodates air springs. The company also offers numerous options, including antiroll bars and numerous brake and spring/damper packages.
If you own a 1966-and-earlier truck you’re probably shaking your fist in the air beckoning why you’ve been overlooked. “They’re almost the same frame!” you’re probably saying. And you’re right. AME has your back, though; it’s tweaking the front mounting points as we speak to offer one for the 1963-1966, “… and 1973-1987 shortly after that,” Craig says. Plans don’t call for a chassis for 1960-1962 trucks as the difference in cab-mounting points and limited number of those trucks makes tooling up a financial folly. However, the primary difference is in the front cab-mounting spread and those cabs are fairly easy to modify.
Craig and Jones admit that it took a long time to bring a 1967-1972 C-series frame to market, but they’re quick to point out why: the truck was a major departure from the other trucks on the market. But if history proves anything, these chassis will revolutionize the GM pickup market. And if past performance is any indicator, we expect the revolution will be significant.