The invention relates to a drive train of a vehicle, comprising a permanently driven primary axle and a secondary axle connectable to the primary axle via a switch-on device with a switch-on mechanism, whereby the secondary drive train output via side shaft couplings is transferred to the drive wheels of the secondary axle.
A disadvantage to these drive trains is that also when the secondary axles are not connected their components are dragged along by the vehicle drive or by the drive wheels rolling away on the roadway, causing power losses. Complete shutdown of the secondary drive train to date is executed only by manually switchable wheel hub couplings which are however a disadvantage with respect to ease of use and practicability.
Because the switch-on mechanism and/or the side shaft couplings have frictionally engaged couplings, it can be that when the secondary axle is uncoupled the section of the secondary drive train located between the switch-on device and the side shaft couplings is uncoupled both from the primary axle and from the secondary drive wheels, such that there is no more power loss in this secondary drive train section, whereby connecting the secondary drive train during travel is possible all the same and losses in comfort and practicability do not have to be tolerated.