Speed reducer for mixer truck and mixing drum driving assembly

The utility model relates to the technical field of mixer truck transmission mechanisms, in particular to a speed reducer for a mixer truck and a mixing drum driving assembly, the speed reducer for the mixer truck is provided with a main input port, an emergency rescue port and an output port, the main input port is used for connecting a main driving power source, and the emergency rescue port is used for connecting an emergency power source. The output port is used for being connected with a speed reducer or a mixing drum of the mixer truck so that power of the main driving power source or the emergency power source can be transmitted to the mixing drum, a plugging cover is detachably arranged at the emergency rescue port, and the plugging cover is used for being detached when the main driving power source breaks down so that the emergency power source can be connected to the emergency rescue port; and the emergency rescue port reserved on the speed reducer is utilized, so that a corresponding matched emerge