Six Decades Ago, General Motors Made Semi Trucks Carry More Weight By Turning The Truck Into A Cracker Box

Trucking companies and owner-operators have long been on a relentless quest to save money. If they can stretch that dollar just a little further, it can mean bringing a little more money. One of the best ways to pad a trucker’s bottom line is through getting them to drive an advanced semi, and in 1959, General Motors built what was, at the time, America’s most advanced semi-tractor. The GMC DLR 8000 and DFR 8000, nicknamed the ‘Cracker Box’ for its shape, were miles ahead of the competition and promised to fill the pockets of truckers, but did so at the expense of practically everything but hauling capability.

Most of the semis that I have written about thus far were built as solutions to high fuel prices and gas crunches. The engineers of those trucks were obsessed with gaining fuel efficiency through aerodynamics. But before the 1970s and its infamous oil crises, aero wasn’t as much of a concern. Instead, truckers were more concerned with maximizing the size of their loads within the restrictions set by state governments.

In the decades preceding the formation of national standards of tractor-trailer length and weight in the 1980s, the states set their own rules. In 1913, at least four states had truck weight limits. In those early days of regulation, a truck driving through Maine couldn’t weigh more than 18,000 pounds, while a truck in Massachusetts was allotted 28,000 pounds. Pennsylvania’s and Washington’s limits were 24,000 pounds. These early weight limits existed because heavy trucks tore up the rudimentary roads of the era.

The U.S. Department of Transportation notes that it wasn’t long after those early days when states began imposing limits on truck lengths, widths, and heights. By 1929, most states had some sort of regulation limiting the size of a truck. Length limits varied wildly, but at least most states agreed on 96 inches as a maximum width. By 1933, every U.S. state had limited truck size and weight in some way.

These length limits were imposed on the whole tractor-trailer and were sometimes ridiculously harsh. As Curbside Classic notes, the railroad lobby once successfully convinced Illinois to limit the total length of a tractor and trailer to just 35 feet. Allegedly, the idea was that if trucks were too short to be an efficient method to move cargo, more freight could be shipped by rail. This would remain the law in Illinois until the federal government stepped in with standardized trailer lengths.

All of this meant that if you wanted to maximize your load and therefore maximize your profit, you had to get clever. This is why the cabover semi ruled American roads from the earliest days of trucking until just after the relaxation of length limits in the 1980s. Cabover semis were shorter than conventional semis, which meant that truckers could carry larger loads. This is why we’ve seen wild builds like a car carrier truck that placed cars between the cab and the engine, and a truck that tried to maximize space by being all trailer.

In the 1950s, General Motors saw length and weight restrictions as an opportunity to build the ultimate truck. It would build a truck that weighed dramatically less than the competition and be so small that truckers could carry a greater payload with a GMC truck than with the competition.

How GM Used To Build Trucks

America’s automakers no longer participate in the Class 8 semi market, but for several decades, General Motors, Ford, and Chrysler didn’t just sell big rigs – they tried to beat the likes of Peterbilt, Freightliner, and Kenworth at their own game. Truck builders constantly one-upped each other in bids to win truckers over. To understand how GMC ended up with its iconic ‘Cracker Box,’ let’s take a look at what came before.

The immediate predecessor to the Cracker Box is the truck affectionately known as the ‘Cannonball.’ As Hemmings writes, this generation of GMC Class 8 tractors dates back to 1947, when GMC introduced new designs after World War II. These cabover trucks went by official designations like HDF for diesels and 620 for gasoline trucks and had designs similar to GM’s lighter-duty Advance Design trucks. According to the American Truck Historical Society, the most famous of the line was the DW 950:

Part of GMC’s top-tier lineup from 1947 through 1954, the 950 series came in two distinct forms: the DW 950, a conventional long-hood tandem-axle tractor, and the DFW 950, its forward-control (cab-over-engine) counterpart. Both were designed to move serious freight, but each played to its strengths—the DW for long, open highway runs, and the DFW for tight quarters, steep grades, and urban maneuvering.

Regardless of configuration, the heart of these trucks was the Detroit Diesel 6-71, a two-stroke inline-six that quickly became one of the most iconic engines in American trucking. Introduced in 1938 and produced through 1995, the 6-71 earned nicknames like Screaming Jimmy, Driptroit, and simply the Detroit, thanks to its distinct sound and reputation for durability (and the occasional oil leak).

In a DW 950, the 6-71 typically paired with a 5-speed main and 4-speed auxiliary transmission ideal for long-haul operators running heavy loads across states or regions. The DFW 950, meanwhile, could be outfitted with a 10-speed constant-mesh transmission for mountain climbs and frequent shifting, often seen pulling doubles in fleet service.

According to former GMC engineer and GMC historian Donald E. Meyer, GM’s next evolution of this generation of truck came in 1955 with the DF 860. GMC touted these trucks as being able to haul more loads for cheaper than ever before. Much of that was due to what was under the cab, a 7.0-liter Detroit Diesel 6-71SE straight-six diesel that delivered 190 HP gross (173 HP net) and 508 lb-ft of torque. GMC bragged that its engine punched out this power at an easy 2,000 RPM and without supercharging.

One of the truck’s highlight features was its non-tilting steel cab with a special way to service the engine. Since the cab couldn’t tilt, GMC gave the truck an interior with fold-up seats and flip-up floorboards. This next part gets a little fuzzy, but in 1958, this generation of truck became famous for its appearance in the TV series ‘Cannonball.’ That’s where the truck’s nickname comes from. Donald E. Meyer says that the DF 860 is the Cannonball, while the American Truck Historical Society says the Cannonball was the 950. So far as I can tell, it seems a lot of folks just consider the whole generation to be ‘Cannonball’ trucks.

But I suppose that isn’t super relevant because it’s what came next that we’re here for.

The ‘Cracker Box’

The Cannonball trucks were followed up by the Cracker Box trucks, officially the DLR 8000 and DFR 8000 cabovers. These big rigs came from that fascinating time in the late 1950s and early 1960s when General Motors punched out moonshot projects worthy of admiration.

Curbside Classic rightfully points out that these Class 8 tractors were surrounded by greats like the Chevrolet Corvair, the Oldsmobile Jetfire, and the Pontiac Tempest, plus engineering achievements like Buick’s aluminum V8, the short-lived ‘rope drive’ system for the Tempest, and the Turboglide three-speed automatic. Don’t forget other icons like the Corvette Sting Ray and the Chevrolet Nova. General Motors embraced the new Jet Age in stride, optimism, and innovation, and its heavy trucks did not miss out.

For 1960 DLR 8000 and DFR 8000, which launched in 1959, GMC decided to go all-in on increasing the profits of the driver at all costs. To facilitate this, GMC focused on lowering weight and shortening length. As I said earlier, there were strict length and weight limits on trucks back then, and the best way to increase loads was to minimize the truck.

One of the highlights of the GMC DLR 8000 and DFR 8000 was its cab. The truck’s BBC, or bumper to back of cab, was just 48 inches. That’s a shockingly small cab, and its comically small size resulted in a visual that resembled a cracker box tilted up onto its side. Amazingly, GMC even sold a sleeper version of this cab, but it came with a puny 21-inch wide bed, so I could not imagine that driving this rig long haul was anything resembling comfortable. However, GMC claimed to have done testing and said that even the tallest drivers had no problems fitting into the cab.

But making the cab small wasn’t the only part of the recipe. Unlike its predecessor, the cab eschewed steel for aluminum, which shaved off tons of weight to become a svelte 696 pounds. Trimmings, like fenders and the grille, were fiberglass. This cab was now of the tilt variety, as well. GMC touted further weight savings with its new Detroit Diesel 6V-71, which weighed 200 pounds less than the previous generation, and the new fabricated frame, which shaved an additional 300 pounds from the Cannonballs. Apparently, the frame alone, which was built in a welded ‘I’ beam configuration, was half the weight of the old Cannonball frame.

According to the Commercial Car Journal, which broke the news of the new truck series in 1958, the trucks had a curb weight of 9,987 pounds with 100 gallons of diesel fuel.

In case you were wondering, here was the difference between the DLR 8000 and the DFR 8000, from Fleet Owner:

Companion model to the DFR-8000 is the DLR-8000 with front axle set back 50 in. from front bumper. The DFR-8000 has a front axle position of 28 in. from the front bumper.

Despite the weight savings, GMC says the new frames, which were made out of SAE 950 steel, were much stronger than the Cannonballs. Other goodies in the DLR 8000 and DFR 8000 trucks included an optional air suspension, an independent short arm long arm suspension with ball joints, and a standard 108-inch wheelbase, with an optional 130-inch wheelbase. Add it all up, and GMC says that the new trucks could carry 2,000 pounds more (76,000 pounds total for combinations) than their predecessors and between 699 pounds and 2,097 pounds more than the conventional models. That, GMC says, was supposed to add $2,000 in profit ($22,114 in 2025) a year for a trucking company or an owner-operator.

Under The Power Barn

The Cracker Box trucks also got a wide array of healthy power options. The aforementioned 6V-71 was a 7.0-liter two-cycle V6 diesel with 189 gross HP on tap at 1,800 RPM with an optional upgrade to 210 HP. Available power also included the 9.3-liter Detroit Diesel 8V-71 V8 diesel, and Caterpillar and Cummins engines would be available later on. If you ordered one of these rigs with a standard drivetrain, you got a five-speed Spicer manual transmission with synchromesh and a two-speed Eaton rear axle.

The coolest engine, at least from a car enthusiast perspective, was the 702-cubic-inch V12. Our Thomas Hundal has written about that engine before:

See, in the late 1950s, diesel commercial engines were gaining market share and GMC wanted to fight back with gasoline power. The answer was simple: Take two existing engines and sort-of glue them together to create something borderline obscene. After some thought, engineers decided on merging wo 351 cubic-inch V6 engines together to create a 11.5-liter V12. Granted, the V12 does sport its own unique block, crankshaft, and camshaft, but the cylinder heads are exactly the same as on the V6. Yes, this means the Twin-Six has four cylinder heads and four exhaust manifolds, along with the expected two distributors.

Oh, but the insanity doesn’t stop there. The crankshaft alone weighs 180 pounds, the wristpins for the pistons measure more than an inch in diameter, the oiling system demands 16 quarts of black gold, the water pump pushed two gallons a second, three thermostats helped keep this thing at operating temperature, and the entire engine weighs nearly 1,500 pounds. Engine length? Try 53 inches long.

All this monstrous size added up to — wait for it — 275 horsepower at launch. That doesn’t sound impressive, but peak horsepower hit at 2,400 rpm. Peak torque was a burly 630 lb.-ft. from 1,600 to 1,800 rpm, an astonishing figure for a gasoline-powered commercial engine from the 1960s. GMC advertised this engine for use in both commercial vehicle and stationary applications, claiming it would run up to 200,000 miles between major overhauls in a period advert. Another claim? That the Twin Six was the cheapest way possible to pump 1,500 gallons of water per minute. Hello, fire department?

A Spartan Hard Worker

Heavy Duty Trucking Magazine notes that the Cracker Box was the poster child of semi-tractor development of the era. It was ugly, spartan, and uncomfortable – but it had no problem pulling absolutely gargantuan loads within the strict legal requirements of the day. Apparently, they were also easy to repair and dependable. If you didn’t care at all about comfort, apparently, the Cracker Box did as it said on the tin.

While I could not find a period review, Heavy Duty Trucking‘s Senior Editor Jim Park had firsthand experience with these trucks when they were new, from HDT:

These trucks were not fun to drive. I first ran into one in 1978 or ’79 as my career was just getting started. Being the junior man at this particular company, I had my choice of the trucks parked in the back row of the lot. I picked a 6×2 axle model, with an air-lift pusher axle. No AC, no power steering, and all the noise and heat you could handle coming up through the floor.

The truck had a 238-hp 6-cylinder two-stroke Detroit 6V-71 diesel engine. Being a two-cycle engine, it had one unique attribute: When backing under a trailer to hook up, you had to hit it pretty hard sometimes to ensure you got under it on the first shot. I learned the hard way that if the trailer pushed the tractor out as you were trying to pick it up, it would spin the engine backwards, and the darned thing kept running — but backwards, sucking air in through the exhaust stack and exhausting through the air cleaner. It was pretty strange putting the transmission in first gear and taking off in the wrong direction!

It’s not known exactly how many of these trucks GMC sold between the model’s launch in 1959 and the end of sales in 1968. Heavy Duty Trucking notes that while the Cracker Box might have been America’s most advanced truck at its launch, the rest of the truck manufacturers would eventually catch up, and the Cracker Box would lose its edge.

Ultimately, in 1969, GMC would replace the Cracker Box trucks with the GMC Astro, which would also get a Chevrolet version with the Titan. These trucks traded the extremes of the DLR 8000 and DFR 8000 for far more interior room, better comfort, slightly better aerodynamics, improved visibility, and more.

What’s interesting is that, despite once being America’s most advanced truck, the Cracker Box is largely forgotten today. If you find one for sale on Facebook Marketplace, don’t be surprised if it’s less than $10,000 or even less than $5,000. So, it doesn’t seem like there are people rushing to snatch these trucks up for collections like they would a Dodge Bighorn or some other trucking icon. But hey, that’s not bad if you’re like me and you’re crazy enough to collect commercial vehicles!

Still, it shouldn’t be discounted what GMC achieved. When faced with tough regulations, it found a way to give truckers a ride that hauled more loads, and did so with an obsession for minimizing to the maximum. It’s just another example of that ambitious spirit that seemed to fuel General Motors back in those days.

Top graphic images: GMC; Nabisco