Abstract: An extension coupling releasably interconnects a trailer to a tow hitch on a tractor vehicle. The apparatus includes a trailer mounting assembly adapted to releasably interconnect to the trailer. The trailer mounting assembly includes a hitch box mount adapted to be secured to a hitch box of the trailer. The trailer mounting assembly also includes an extension coupling which has a proximal end portion secured pivotally to the hitch box mount about a pivot axis. The extension coupling terminates in a distal end portion, and the distal end portion is provided with a pair of oppositely projecting trunnions that extend along a load axis that is perpendicular to the pivot axis. The apparatus also includes a tow hitch assembly adapted to be secured to the bed of a tractor vehicle. The tow hitch assembly includes a pair of spaced apart receivers sized and oriented to engage the trunnions of the extension coupling to define an engaged state.