Triple Cone Synchronizer Operation

The synchronizer is operated by a hydraulic piston with pressure supplied from RDU pump via the hydraulic supply lines connecting the PTU to the All Wheel Drive (AWD) valve block. Solenoid operated spool valves in the AWD valve block direct hydraulic pressure to the piston in the PTU casing to engage or disengage the triple cone synchronizer. A spring loaded detent locks the synchronizer selector fork in either position, removing the requirement for hydraulic pressure to maintain to hold the synchronizer piston in the required position.

The All Wheel Drive Control Module (AWDCM) controls the operation of the active driveline system and the operation of the PTU synchronizer hydraulic operation.

The synchronizer process comprises a number of steps from disengagement to full engagement.

1. When the transmission differential is rotating the input shaft, the engagement ring integral with the input shaft is also rotating. With the synchronizer disengaged no drive is transmitted to the crown wheel shaft and the crown wheel drive gear, the pinion drive gear and the drive flange remain stationary.
2. When engagement is required, hydraulic pressure is applied to the piston and the synchronizer selector fork begins to move the synchronizer sleeve in the engagement direction. The selector fork moves the synchronizer sleeve in an axial direction and the synchronizer detents contact the blocker ring. This starts to align the blocker ring teeth with the teeth on the synchronizer sleeve.
3. As the synchronizer selector fork continues to move axially, the friction caused by the detents between the synchronizer sleeve and the blocker ring reduces the speed of both components until they are rotating at the same speed. The teeth of the synchronizer sleeve now start to mesh with the teeth on the blocker ring.
4. With the blocker ring and the synchronizer sleeve rotating at the same speed, the sleeve fully engages with the blocker ring teeth. However, there is still a speed difference between the input shaft engagement ring and the synchronizer sleeve. This speed difference is reduced as friction surfaces (cones) between the input shaft synchronizer sleeve and the blocker ring start to mesh.
5. The synchronizer selector fork now moves the synchronizer sleeve axially into contact with the teeth of the input shaft engagement ring. The tapered teeth of both components now start to mesh and the synchronizer sleeve rotational speed is increased as it starts to engage with the engagement ring.
6. When the synchronizer sleeve is fully engaged with the input shaft engagement ring, the rotational speed of the input shaft and the crown wheel shaft are the same and drive is passed via the crown and pinion drive gears to the drive flange.
7. Disengagement is a reverse of the engagement process. When the synchronizer selector fork moves the synchronizer sleeve fully out of engagement with the engagement sleeve and the blocker ring, it touches the casing. Friction between the casing and the synchronizer sleeve brakes the crown wheel shaft and drive gear, the pinion drive gear and the drive flange to prevent them from rotating through oil drag between the components.