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Amphibious Encyclopedia · Military amphibians

Ford GPA "Seep"

The Ford GPA, nicknamed the Seep, was an amphibious version of the World War II jeep, built by Ford in 1942 and 1943 [1][5]. About 12,778 were made, but the GPA proved too heavy and too low in the water for most military work, and production stopped early in 1943 [3][5]. Many went to the Soviet Union, and surplus examples later carried adventurers, most famously Ben Carlin's Half-Safe [3][5].

  • Military amphibians
  • 1942 to 1943
  • United States

Development

After the U.S. Army ordered its first jeeps in 1941, the National Defense Research Committee started a project for a light amphibious quarter-ton truck, known as the QMC-4 [5]. Ford drawings for the QMC-4 Amphibious Scout Car are dated February 1942 [2]. Yacht designer Roderick Stephens Jr. of Sparkman & Stephens shaped the hull, which looked like a small version of the larger DUKW amphibious truck [5].

Ford and Marmon-Herrington built competing prototypes. Marmon-Herrington used an all-steel unit body, while Ford built its hull around the frame of its GPW jeep. Ford's design was about 400 lb (180 kg) lighter and cheaper to build, and it won the production contract in 1942 [3][5]. Ford called the vehicle the GPA, and soldiers called it the Seep, a name usually explained as a blend of sea and jeep. The nickname was never official [3][4].

Design

The GPA used the jeep's 134 cu in (2.2 L) four-cylinder side-valve engine of 60 hp, with a three-speed gearbox and a two-speed transfer case for four-wheel drive [3][5]. In the water, a power take-off turned a propeller in a tunnel under the stern, and a rudder steered. A bilge pump and a capstan winch on the bow were standard [3][5]. The GPA was 15 ft 2 in (4.62 m) long and 5 ft 4 in (1.63 m) wide [4]. The Museum of the American G.I. gives top speeds of 50 mph (80 km/h) on land and 5.5 mph (8.9 km/h) in water [4].

The vehicle ended up much heavier than planned. Ford's own records say it weighed about 800 lb (360 kg) more than the land jeep [1], and Wikipedia gives 2,450 lb (1,110 kg) empty and 3,550 lb (1,610 kg) fully loaded [5]. The added weight was not matched by more hull volume, so the GPA floated low in the water [5].

Service

The Henry Ford says Ford built 12,781 amphibious jeeps at its Rouge plant in 1942 and 1943 [1]. Other sources give 12,774 or 12,778 [4][5]. In service the GPA disappointed. Its low freeboard limited it to calm water and small loads, inadequate bilge pumps let it fill in moderate seas, and it swamped easily in surf [3][5]. On land it was heavy and clumsy and often got stuck [3][5]. It worked well enough for river crossings in calm water [3].

GPAs saw limited use in North Africa and the Pacific and took part in the 1943 Allied landings on Sicily, where their limits became clear [3][5]. Production stopped in March 1943, which Wikipedia attributes to financial disputes with the government and poor reports from the field [5].

Lend-Lease and the Soviet copy

About 4,486 GPAs went to Allied countries under Lend-Lease, including 3,520 to the Soviet Union and 852 to the British Commonwealth [5]. The Soviet Union later built its own amphibious jeep closely modeled on the GPA, the GAZ-46, which entered production in 1952 [3][5].

Legacy

After the war, surplus GPAs were sold to farmers, ranchers and adventurers, and collectors began restoring them in the 1970s [3][4][5]. The best known is Half-Safe, the heavily modified GPA in which Australian Ben Carlin traveled around the world in the 1950s [3][5]. Wikipedia estimates that about 200 GPAs survived into the 21st century, while the Museum of the American G.I. puts the figure at about 250 [5][4]. One well-preserved example sold at auction for US$125,000 in 2016 [5].

Sources

  1. Ford GPA Amphibious Jeep, 1943, The Henry Ford. www.thehenryford.org/collections/explore/artifact/33777
  2. Drawing, "Q.M.C.-4 Amphibious Scout Car," Ford GPA, February 16, 1942, The Henry Ford. www.thehenryford.org/collections/explore/artifact/524305
  3. The Ford GPA, Military Trader (Steve Turchet) (2023-10-11). www.militarytrader.com/mv-101/the-ford-gpa
  4. Ford GPA Seep (1942-1943), Museum of the American G.I.. americangimuseum.org/collections/restored-vehicles/ford-gpa-seep-1942-1943
  5. Ford GPA, Wikipedia. en.wikipedia.org/wiki/Ford_GPA

Last reviewed November 2026. Spotted something to correct or add? Tell us and include a source.

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