TANDEM AXLE WITH DISCONNECT COAST

1 . A method of disconnecting and connecting elements of a tandem axle system drivingly connected to an engine and transmission of a vehicle, the method comprising the steps of:

providing a tandem axle system comprising:

an inter-axle differential and clutch assembly in driving engagement with the engine, wherein the inter-axle differential and clutch assembly comprises an inter-axle differential and an inter-axle differential lock;

a forward axle assembly comprising a differential assembly, a disconnect assembly and two axle half shafts, wherein the disconnect assembly selectively connects the axle half shafts to the differential assembly; and

a rear axle assembly comprising a differential assembly, a disconnect assembly and two axle half shafts, wherein the disconnect assembly selectively connects the axle half shafts to the differential assembly;

providing a control system in communication with the inter-axle differential lock, the disconnect assemblies and the engine;

detecting a disconnect opportunity;

commanding the engine torque set to zero;

disconnecting one or both of the axle half shafts of the forward and rear axle assemblies;

engaging the inter-axle differential lock; and

allowing the engine to idle.

2 . The method of claim 1 , wherein the disconnect opportunity is further detected when the vehicle has reached a predetermined cruise speed or the vehicle has reached a predetermined torque limit.

3 . (canceled)

4 . The method of claim 1 , wherein the step of engaging the inter-axle differential lock occurs before disconnecting the axle half shafts of the forward and rear axle assemblies.

5 . The method of claim 1 , wherein the step of engaging the inter-axle differential lock occurs simultaneously with disconnecting the axle half shafts of the forward and rear axle assemblies.

6 . The method of claim 1 , further comprising the steps of:

detecting a reconnect opportunity;

matching rotational speeds of the axle half shafts of the forward and rear assemblies;

reconnecting the axle half shafts of the forward and rear assemblies;

disengaging the inter-axle differential lock; and

returning control of the engine back to the operator of the vehicle.

7 . The method of claim 6 , wherein the reconnect opportunity is detected when the vehicle has slowed to a predetermined axle reconnect speed or the vehicle has reached a predetermined torque limit.

8 . (canceled)