Meet the GMC DUKW, aka the “Duck”
While amphibious vehicles were built before, the 1942-’45 GMC DUKW (a.k.a “Duck”) was one of the first to be pressed into military service for the United States. The DUKW was, for the most part, a boat built around a GMC AFKWX, GMC CCKW six-wheel-drive military truck. It could haul men and gear from supply ships to the beaches and further inland, if necessary.
It had a 2.5-ton “at sea” payload capacity.
Assembled in Pontiac, Michigan over 21,000 GMC DUKWs were built during World War II. General Motors and Naval architecture firm Sparkman & Stevens designed the DUKW as a means to approach and cross beaches in amphibious attacks.
Interestingly, the GMC DUKW’s name came from official military/General Motor’s terminology. The D stands for the year (1942), U for utility (amphibious), K for all-wheel drive (or 4WD), and W for 2 powered rear axles. It had a power-takeoff system which worked with a winch and a air-compressor. It had a bilge-pump too. The propeller went through the transfer case and the rear wheels had a seperate two-speed transfer case.
Weighing in at 13,000 lbs in its regular configuration, the GMC DUKW was powered by a 4.0-liter, 94 horsepower GMC Model 270 straight-six engine. It had an on-road top speed of 50 mph and a top speed of 5.5 knots on the water. It had a 400 mile on-road range and a 58-mile range at sea.
The Duck had some issues
While it looked armored, GMC only made the DUKW’s steel plating between 1/16 and 1/8th-inch thick. This was a boat, after all, and it had to be lightweight. At 31 feet long, 8’3″ wide and 7’2″ high, GMC made the DUKW a bit larger than the equivalent troop transport. Its steel rusted terribly and troops had to grease nearly every mechanical component constantly during the vehicle’s time in service.
Among many of the unique innovations that GMC bestowed on the DUKW, the on-board tire inflation system is one of the most noteworthy. At first, whenever a Duck hit the beach, it had to air-down its tire pressure to allow for better traction on beach sand. Once it hit the road, the crew had to air up again to increase overall performance. All of this had to be done, even in treacherous combat conditions, and it was incredibly time consuming. Back then, the term “Sitting Duck” was not lost on the crew of early production DUKWs. Using the Speir’s tire inflation system mitigated the risk and allowed the driver to select from various pressures for any surface, on the move.
After the war, tourism companies repurposed the few GMC DUKWs that didn’t rust into pieces. Even today, several land-and-sea tour companies use the DUKW.
I’ve ridden in a tour version and a restored military version on land and sea. Both times I sat near the front and marveled at the sheer amount of dials and levers. According to one of the drivers, “Once you get used to it, it’s only slightly more complex than driving a regular Army 6X6.”
I think The Fast Lane Truck needs one of these amazing trucks – soon.