Disconnectable driveline for all-wheel drive vehicle

1. A drivetrain for an all-wheel drive motor vehicle, the drivetrain comprising:

a differential input that is rotatable about a first axis;

a differential assembly having a differential case and a differential gearset, the differential case being coupled to the differential input for common rotation about the first axis, the differential gearset being housed in the differential case and being configured to receive rotary power therefrom, the differential gearset having a pair of differential output members;

a power take-off unit (PTU) having an input spindle, a spool, a ring gear, and a dog clutch, the input spindle being coupled to the differential case for common rotation about the first axis, the spool being disposed concentrically about the input spindle, the ring gear being fixedly coupled to the spool, the dog clutch having first and second dog members, the first dog member having a first set of dog teeth that are disposed circumferentially about the first axis, the first dog member being fixedly coupled to one of the spool and the input spindle, the second dog member having a second set of dog teeth that are disposed circumferentially about the first axis, the second dog member being non-rotatably but axially slidably coupled to the other one of the spool and the input spindle, the second dog member being movable along the first axis between a first position, in which the second set of dog teeth are disengaged from the first set of dog teeth to thereby inhibit transmission of rotary power between the input spindle and the spool, and a second position, in which the second set of dog teeth are engaged to the first set of dog teeth to thereby permit transmission of rotary power between the input spindle and the spool; and

a shaft member coupled for rotation with one of the differential output members and extending through the input spindle.

2. The drivetrain of claim 1 , further comprising an actuator that is configured to selectively move the second dog member.

3. The drivetrain of claim 2 , wherein the actuator comprises a fork that is received in a groove formed in the second dog member.

4. The drivetrain of claim 1 , wherein the input spindle extends completely through the spool.

5. The drivetrain of claim 4 , wherein the PTU further includes a housing in which the spool is rotatably received, and wherein a pair of seals engage opposite ends of the input spindle, each of the seals forming a seal between the housing and the input spindle.

6. The drivetrain of claim 5 , wherein the PTU further includes a pair of input spindle bearings that are directly mounted to the housing and the input spindle, and wherein the input spindle bearings are disposed along the first axis in a first zone that is disposed between the seals.

7. The drivetrain of claim 6 , wherein the PTU further includes a pair of spool bearings that directly engage the housing and the spool to support the spool for rotation about the first axis, and wherein the spool bearings are disposed along the first axis in a second zone that is disposed between the input spindle bearings.

8. The drivetrain of claim 7 , wherein the dog clutch is disposed within the first zone but not within the second zone.

9. The drivetrain of claim 8 , wherein the ring gear is disposed along the first axis between the differential case and the dog clutch.

10. The drivetrain of claim 4 , wherein the PTU further includes a housing in which the spool is rotatably received and a pair of input spindle bearings, each of the input spindle bearings being engaged directly to the axle housing and the input spindle.

11. The drivetrain of claim 1 , wherein the ring gear is disposed along the first axis at a location between the differential case and the dog clutch.

12. A drivetrain for an all-wheel drive motor vehicle, the drivetrain comprising:

a differential assembly having a differential case and a differential gearset, the differential case being rotatable about a first axis, the differential gearset being housed in the differential case and being configured to receive rotary power therefrom, the differential gearset having a pair of differential output members;

a power take-off unit (PTU) having a housing, an input spindle, a pair of input spindle bearings, a spool, a pair of spool bearings, a ring gear, and a dog clutch, the housing defining a cavity into which the input spindle, the spool, the ring gear and the dog clutch are received, the input spindle being coupled to the differential case for common rotation about the first axis, the input spindle bearings being mounted to the housing and the input spindle and being configured to support the input spindle relative to the housing, the spool being disposed concentrically about the input spindle and supported relative to the housing by the spool bearings, the ring gear being fixedly coupled to the spool, the dog clutch having an axially fixed dog member and an axially movable dog member, the axially fixed dog member being fixedly coupled to the spool and having a first set of dog teeth that are disposed circumferentially about the first axis, the axially movable dog member having a second set of dog teeth that are disposed circumferentially about the first axis, the axially movable dog member being non-rotatably but axially slidably coupled to the input spindle for movement along the first axis between a first position, in which the second set of dog teeth are disengaged from the first set of dog teeth to thereby inhibit transmission of rotary power between the input spindle and the spool, and a second position, in which the second set of dog teeth are engaged to the first set of dog teeth to thereby permit transmission of rotary power between the input spindle and the spool; and

a shaft member coupled for rotation with one of the differential output members and extending through the input spindle.

13. The drivetrain of claim 12 , wherein the ring gear is disposed along the first axis between the spool bearings.

14. The drivetrain of claim 12 , wherein the spool bearings are disposed along the first axis between the input spindle bearings.

15. The drivetrain of claim 12 , wherein the PTU further comprises a pair of seals, each of the seals being sealingly engaged to the housing and the input spindle.

16. The drivetrain of claim 15 , wherein the spool bearings and the input spindle bearings are disposed along the first axis between the seals.

17. The drivetrain of claim 12 , wherein the axially movable dog member is disposed between an outboard one of the spool bearings and an outboard one of the input spindle bearings.

18. The drivetrain of claim 12 , wherein the input spindle defines a male splined segment on which the axially movable dog member is non-rotatably but axially movably mounted, and wherein the male splined extends along the first axis into the axially fixed dog member.

19. A drivetrain for an all-wheel drive motor vehicle, the drivetrain comprising:

a differential assembly having a differential case and a differential gearset received in the differential case, the differential case being rotatable about a first axis, the differential gearset having a pair of differential outputs;

a power take-off unit (PTU) comprising input spindle means coupled for rotation with the differential case, spool means concentrically disposed about the input spindle means, a ring gear mounted to the spool means, and clutch means for selectively coupling the input spindle means and the spool means; and

a shaft member coupled for rotation with one of the differential outputs and extending through the input spindle means.