Abstract: An improved trailer is provided for use with an automotive draft vehicle. The trailer is of the class including a coupling member attached on its forward end to a draft vehicle and having a trailer rear axle assembly slidably mounted on the rear end so as to be movable longitudinally along the coupling pole between predetermined long-coupled and short-coupled positions to thereby adjust the effective length of the trailer. Improved coupling assemblies are also provided for adjusting the effective length of the trailer and maintaining the rear axle assembly in the adjusted positions.