With the beginning of the Advance Design trucks in 1947, GM introduces the first major gas tank location change since 1936! It was taken out of the cab on ½ tons and placed under the bed.
To save costs, GM designed one gas tank to fit a ½ ton pickup, panel truck, Suburban, and Canopy Express (not the same on ¾ ton). In theory it was a good money saving decision, however in the real world it was not successful. The tank was placed back in pickup cabs in 1949!
GM engineers appear to have not considered the abuse and overloading given the American pickup truck. On the farm and in construction use, the pickup was often used beyond its rated capacity.
It took little time for GM to discover their ½ ton under bed gas tank was positioned to receive major rock damage. Tanks often became punctured when the truck was in deep ruts of poor roads or used in the farm fields.
With the many dirt and gravel roads deep grooves from the tires could develop during rains or a spring thaw. This was often the case beside fields where trucks and farm tractors created deep ruts. Driving in these groves lowered the truck and the under bed gas tank became closer to the road center. An increased exposure occurred when the pickup was heavily loaded. The tank became even closer to the road center and was more of a target for protruding rocks. Just overloading a 1947-48 ½ ton pickup in a high grassy pasture was exposing the tank to contact by hidden objects.
Truck owners complained to the dealers and GM’s quality control department finally recognized the problem. By 1949, pickups were introduced with their gas tanks placed back in the cab. They remained there until the new body style of 1973.
Because the single unit body (Suburban, Panel Trucks, and Canopy Express) usually received less use in the field, their gas tank location was kept the same through the end of the series in mid-year 1955. Thus, the 1947-48 ½ ton gas tank is the same as on 1947-55 single unit bodies.
By placing them back under the 1973 pickup bed (this was a strong safety requirement by the US Government) GM created even a more dangerous problem because they were attached to the outside of the frame rail! Of all dangerous places, it was only protected by the lower section of the sheet metal bedside. If being hit broadside collision, in the correct place, gasoline could be forced out in all directions. Are sparks created in a broad side collision? Hmm!