Does the gearbox calibrate o.k.? Any error codes? Do you have any other gear change faults?
When making the gear change you discribe The B range/reverse synco moves to neutral and the a/c range syncro moves from neutral to engages into c range plus clutch pack changes.
The fault could be machanical, hydraulic or electrical.
More info required. I would check the synco rail pots and rail movement and check the pressures in the syncos
Ash
December 2011