Variable hydraulic pump for a transmission and method of operating

There is provided a binary pump with constant displacement for a drive train of a vehicle. A hydraulic system operably connected to a first and a second outlet port of the pump and serves to alternately permit fluid flow through both outlet openings allow (ie, full displacement or full discharge capacity of the pump), or a flow through only the first outlet opening (ie, partial displacement or partial discharge volume of the pump). The pump can be housed in the front carrier of the transmission. It may be provided an auxiliary pump that serves to supplement the output of the binary pump or to be used if the binary pump is turned off. There is provided a method for operating the binary pump and the auxiliary pump.