Abstract: This invention provides a common means of coupling an alternative power source to a vehicle's drive wheels which is particularly well suited for use with a countershaft-type transmission. This invention also addresses clutch wear by eliminating the need to engage the frictional clutch to launch the vehicle. This invention also improves the acceleration of the vehicle compared to a typical dry friction clutch launch by relying on the HLA system to transfer more power to the drive wheels more quickly than would be transferred by a typical launch engagement of a dry friction clutch in a commercial vehicle.