The Ford GPA 'Seep' (from Seagoing Jeep), was an amphibious version of the WWII Ford GPW Jeep. Unlike the jeep, the seep was not a successful design being too slow and heavy on land and lacking sufficient seagoing abilities in open water. Similar design features were used in the larger and more successful DUKW amphibious truck.
History and Development
After having commissioned Willys, Ford and Bantam to build the first 4,500 jeeps (1500 each) in March 1941, the US Motor Transport Board set up a project under the direction of the National Defense Research Committee (NDRC) to be designated "QMC-4 1/4 Ton Truck Light Amphibian".
The War was on at full tilt, and with bridges over Europe's rivers being taken out one after another, it seemed practical if the jeep could swim as well as drive. And so it came to Roderick Stephens Jr. of Sparkman & Stephens Inc. yacht designers, to design a shape for a 2700 lb (1,200 kg) amphibious jeep, in the same vein as his earlier design for the DUKW six-wheel-drive amphibious truck. Not surprisingly Stephens' hull design looked like a miniature version of that of the DUKW, and just like it, the 'Seep' was going to have a screw propellor, driven by a power take-off, operating in a dedicated tunnel faired into the rear end bodywork, as well as a proper rudder.
The construction of the vehicle was developed in competition by Marmon-Herrington and Ford Motor Company. Marmon-Herrington specialised in all-wheel drive vehicles. The Marmon-Herrington prototype's hull formed an integral unibody structure, created by cutting shapes out of steel plate and welding those together, much like the hull or chassis of an armoured vehicle. The Ford entry however used a sturdy chassis and internal frame, to which more or less regular automobile type sheet-steel was welded. This construction made the GPA some 400 lb (180 kg) lighter than its competitor. Also The GPA's design was based on the Willys MB and Ford GPW standard Jeeps as much as possible. When designing and building the GPA, Ford utilized many of exactly the same parts that the Ford GPW did. The GPA had an interior similar to that of the MB/GPW jeeps, although the driver's compartment had almost twice as many control levers: 2WD/4WD, hi-range/lo-range, capstan winch (on the bows), propeller deployment and rudder control. After a direct comparison of the two company's prototypes, Ford received a contract for production starting in 1942.
In contrast to the DUKW the GPA (G=Government, P=80" wheelbase, A=Amphibious) did not perform well in the field. At some 1,600 kg (3,520 lbs) the production craft had become much heavier than the original 1,200 kg (2,640 lbs) specified in the design brief, but its volume had not been increased accordingly. As a consequence a low freeboard in the water meant that the Seep couldn't handle more than a light chop, and certainly couldn't take much cargo. The Seep's intended objective: to ferry soldiers to and from ships off-shore, to trundle up the beach and continue inland, was therefore not met. It is reported that many of the Jeeps that were used in battle sank if there were any significant waves at all.
On land the vehicle was too heavy and its body too unwieldy to be popular with the soldiers. Adding insult to injury, the GPA would frequently get stuck in shallow waters, where the regular Willys MB's water fording abilities allowed it to drive straight through (Pohl, 1998). Production was already halted in March 1943 after production of only 12,778 vehicles, due to financial quibbles between Ford and the US government, as well as bad reception of the vehicle in theatre. Although some sources (Pohl; Carlin, 1989) state that less than half of that number were ever completed, serial numbers of surviving specimens suggest that the 12,7XX figure is actually correct.
In spite of participating successfully in the Sicily landings of September 1943, and performing reasonably well in inland river crossings, most GPA’s were routed to Russia under the Lend-Lease program. GPAs were also used in action North Africa, Normandy France, Holland and the South Pacific. They were also used by the British, Canadians and Free French/Fighting French.
The Russians were sufficiently pleased with the GPA's ability to cross rivers and inland waters, to keep developing it after the war. Starting out with the chassis of the GAZ-67B, prototypes were created that largely copied the Seep's layout and design, eventually leading to the GAZ 46 MAV, based on the chassis and mechanicals of the GAZ 69 4x4 jeep, to go into production as of 1952. Both the GAZ 69 and the amphibious GAZ 46 were exported to many communist countries.
By 1944 GPAs were being sold as surplus and were purchased by farmers, ranchers, adventurers and others. By the 1970s collectors had discovered them and started restoring them back to their original specifications. They appear at various military vehicle shows and the Normandy "D-Day" anniversaries in June.
Half-Safe and Other Conversions
After World War II, several adventurers converted surplus GPAs into world-travelling machines.
The most famous one was during the 1950s when Australian Ben Carlin (1912–1981) sailed and drove a modified Seep, that he called "Half-Safe" on a journey around the world.
A young American couple converted one which they called "Tortuga" and travelled from Alaska to the Southern tip of South America. They later converted another one which they called "Tortuga II" which they used in the South Pacific.
A World War II British paratrooper veteran named Lionel Force purchased a GPA from Levy's Surplus in Toronto, Ontario, Canada, and called it "The Amphib." Among the many changes he grafted on a roof from a Dodge station wagon and lengthened the hull at the stern. He used the top halves of the doors, but knowing that he might be tied up alongside a dock, he added a round roof hatch on the top. He planned to travel from Toronto to England via the USA, Mexico, Guatemala, Panama, South Armerica including Brazil, Africa, the Middle East, Greece and up to England. He got as far as Panama but turned back when he learned that the freighter upon which he intended to ship "The Amphib" from Brazil to Africa had been taken out of service.
Replicas of the GPA are featured in the 2007 Film Indiana Jones and the Kingdom of the Crystal Skull. Custom built by Ghostlight Industries of San Fernando, California, the fiberglass bodies were intentionally constructed 10% larger than the actual vehicle to ease filming.