(updated 12/31/2020 to acknowledge that the DFR8000 was actually produced)
Independent front suspension, air-suspension all-round, an ultra-light forward-set alloy cab only 48″ long, power steering, a complex fabricated frame that was 50% lighter, and the lightest diesel engine: This was the recipe for the most technologically advanced semi truck tractor in the world in 1959. It could haul over a ton of extra payload capacity thanks to its light weight, it was highly efficient and was the most comfortable for its driver.
The DLR/DFR 8000 sprung from the same mindset that created the air-cooled rear-engine Corvair, the “rope-drive” Tempest, Buick’s Aluminum V8, turbocharged Cutlass Jetfire, the Turboglide, and a raft of other engineering firsts at GM in the years 1959-1962. None of these survived long-term, and most were gone within a couple of years, including these GMC DLR/DFR 8000s. Intended to vault the competition through sheer technical overkill, they were the result of the oft-deadly hubris that permeated GM. In this case, the failure of the DLR/DFR 8000 led to the GMC Truck division’s terminal decline in the heavy duty field.
The GMC “crackerbox” COE did survive longer, until 1969, but only because a very conventional dumbed-down version was rushed into production to replace the DLR/DFR 8000, not unlike the 1962 Chevy II and 1964 Tempest, Skylark and Cutlass. Turns out what American truckers really wanted was cheap, heavy, average, but good looking, just like American car buyers. How did GM not know this?
COE (Cab Over Engine) trucks became popular in the mid-late ’30s, like this 1937 GMC semi tractor. There were several advantages, the two biggest being better weight distribution and of course a shorter overall length. That become the dominant factor as the trucking industry expanded beyond regional reach and had to deal with an arcane hodge-podge of different length (and weight) regulations in an increasing number of states. The best solution was a short COE tractor to meet the regulations of the most stringent state(s) the truck would have to operate in. Of course there were other advantages too, in maneuverability in urban settings.
This ability to meet the various state restrictions was of particular importance to movers, which had to potentially be able to go to any state, and explain why long distance moving trucks almost invariably had COE tractors.
The truck industry prior to the mid-late ’60s was divided into two markets: the far West, and everything else. That’s because the West Coast had drastically more lenient length rules, so that long conventional trucks like this 1940s Peterbilt dominated there.
Even CEO trucks out West often didn’t take advantage of their space efficiency, like this long wheelbase early Freightliner.
As we shall see, GMC’s DLR/DFR 8000 was clearly targeted to the eastern market.
In the East, the White 3000, the first popular tilt-cab truck dominated the COE market in the ’50s.
International got in the tilt-cab COE market in 1953. It soon spawned other variants.
Meanwhile, GMC, which along with International had for decades been the two top selling medium/heavy-duty truck brands, only had an older style non-tilt COE, dubbed the “cannonball” for obvious reasons. GMC was risking seriously falling behind in what soon came to be the dominant style of semi tractor.
Both front and rear axles were suspended on air bags, resulting in a dramatic improvement in ride quality. The technology came straight from the buses. How many were actually sold with the air ride is another question. Not many, apparently.
But that just was a stop-gap at best. GM’s truck engineers went to work creating the ultimate COE highway tractor, one that would top the competition in every metric: weight, space efficiency, load capacity, and driver comfort. The “Tilt-Cab Cruiser” was first shown at the Chicago Auto Show in December 1958, and only as the cab-forward DLR8000.
This brochure from 1959 shows the DLR 8000 (left) with its aluminum cab in front of the axle and an ultra short 108″ wheelbase, which combined with its mere 48″ of cab length meant that longer trailers could be used in highly restricted states. It also shows the DFR 8000 (right) that was added later that year, which had its cab directly over the front axle, and also sat a bit higher too. According to the brochure, it was available in 108″ and 130″ wheelbase length. A very compact sleeper cab version was available in either configuration.
There’s very little detailed historical information about these trucks except from a few brochures and a few paragraphs at some forums. Even the definite book “GMC Heavy Duty Trucks 1927-1987” has precious little on them. GM press releases state that the DLR 8000 went into production in 1959, and the DFR 8000 was added sometime later in that year. This ad from 1959 only shows the DLR8000. And as we’ll see later, by 1960 a very conventional “crackerbox” with its cab over the axle like the DFR 8000 was added, which quickly became the only version offered.
The DLR 8000 was a clean sheet design from the frame up. Its frame was quite unusual, as instead of the usual riveted C-channel rails with cross members, it was designed some 50% lighter due to being fabricated from specially formed steel components and then welded together. The DLR’s frame (upper left) was quite distinct from the DFR’s frame (lower right) with its deep X member. This was all highly unusual and ambitious. For optimum weight distribution, the DLR came (only) with the inline Detroit Diesel 6-71, and the DFR was came with the new V6-71, since it was shorter and as such would not extend past the rear of the cab.
The very minimalist cab was fabricated mostly from aluminum, with fiberglass fenders and front grille. The sleeper cab added a mere 24″ length; it’s not visible here, but the 30″ wide mattress makes a jog behind the driver’s seat, narrowing it down to 22″.
The two different designs are more obvious here. The DLR’s X-braced frame (left) is even visible.
Here’s a good look at the independent front suspension. A traditional SLA (short arm/long arm) with ball joints.
More details on the front suspension and steering. Power steering was optional, something that was not at all common on big trucks back then, and for quite some time to come.
The standard 6-71 two-stroke diesel engines were rated at 189 gross/175 net hp @1800 rpm (DD diesels only sound like they’re revving fast because of being two strokes), and 577/553 ft.lb. of torque @1200rpm. The optional version with larger injectors had 210 hp. A five speed Spicer “synchromesh overdrive” transmission teamed with a two-speed Eaton rear axle. There was no twin rear axle version, and very few options. This was a very tightly specified truck for very specific applications.
Here’s the DLR specs. Unfortunately, there no weights given here, but I found it elsewhere: 9090 lbs.
The DFR was also available in a longer 130″ wheelbase.
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