Anything and everything GT6.

I have had a problem with the overdrive on my Mk2 since I took ownership. Sometimes it works, sometimes not, mainly not! I thought the problem to be electrical. Anyway having removed the gearbox cover and checked the connections I now get a rapid clicking noise from the solenoid when the ignition is on, the car is in 3rd or 4th and the switch operated. Is this normal or does it mean the solenoid is on the way out?

Any help would be appreciated. Thanks. Jonathan