Triumph Repair: 74 TR6 J Type Overdrive, spider gears, output shaft

Question
I am having trouble with my overdrive unit and not sure the solenoid is working properly.  I have removed the solenoid from the car.  How do I properly test it to see if it is functioning?

Answer
With the piston in it just connect 12v to it and it should operate the piston. Keep in mind that in the car the solenoid does not work except in 3rd and 4th gear.

The output shaft turns a cam the runs a pump to apply fluid pressure to pistons that over ride springs that hold a cone shaped clutch engaged so the input and out put shafts are locked together and when you reach enough speed to get into 3rd gear and activate the OD, the solenoid opens ports to allow fluid to go into the two pistons that will over ride the springs to force the cone shaped clutch away from the input shaft cone and force it into a mounted internal cone which then makes spider gears rotate which in turn drives the output shaft in a higher ratio giving the output shaft a higher gear.
Most of the time you don't have to remove it to test it. Take a 12v lead and with it quiet or sometimes you can just put your fingers on the solenoid and touch the solenoid wire with a 12v test lead and you can hear or feel it "Click".
Howard