Doonan Diamond - Dropdeck Trailer

Drop deck trailers are built much like flatbed trailers, except they have a “gooseneck” which drops the trailer height to a lower level behind the tractor. A drop deck trailer’s lower deck height allows for taller loads, as well as, providing a lower center of gravity for heavy loads. On a drop deck trailer, the gooseneck is general a fixed neck, however, Doonan manufactures drop decks with removable and folding necks as well. Other common names for a drop deck trailers include Drop Deck, Single Drop, Step Deck and Drop.

While drop deck trailers are generally between 48’ and 53’ long and between 96” and 102” wide, Doonan produces them anywhere from 30’ to 60’ in length and 96” to 114” in width. Additional lengths can be achieved by purchasing an extendible drop deck trailer. On an extendible drop deck trailer, the lower deck separates allowing the axles and the rear portion of the lower deck to slide backwards creating an opening in the floor of the trailer. Extendible trailers are typically used for self-supporting loads. Many factors impact the overall length of an open drop deck extendible trailer including closed trailer length, top deck length, number of axles, axle spacing, and overhang. See Doonan’s Extendibles page for various extendible style trailers.

Drop deck trailers are made from steel, aluminum or a combination of both steel and aluminum. The following are Doonan’s four standard models of drop deck trailers. The differentiation between the models is based on the materials