A mounting frame for attaching a backhoe or other implement to a lift arm of a vehicle, such as a compact loader, includes an upright arm on the mounting frame that is positioned ahead of and adjacent to a forward portion of a lift arm of the loader. The upright arm carries a pivoting locking handle at a first pivot and a locking link is pivotally supported on the locking handle on a first pivot pin. The locking link has a second pivot pin that can be moved to be supported in an existing pin sleeve or bushing on the lift arm. The pivot pins on the locking link are positioned so that when the locking handle is moved to a locked position, the line between the axes of the pivot pins on the locking link goes over center with respect to the pivot axis of the first pivot locking handle, and a hook end of the link latches onto a locking projection on the upright arm. The mounting frame is held in a fixed position relative to the lift arm.