Do the VTD transmissions of this vintage experience frequent duty c failures like the ACT-4s do? I would imagine a failure of this solenoid on one of these would cause a fault that would result in no ability to "lock" the center diff. This would probably go unnoticed by the driver in most cases, but if this was a common failure they may have changed the solenoid to try and improve the system's reliability. Just a shot in the dark guess...
