Triumph Repair: Spitfire Overdrive, Triumph, Spitfire

Question
Hi Jim
I have a 78 spitfire.  My overdrive won’t engage until it “warms up” or about five miles if I turn it the switch to off when I park it overnight.  If I remember to flip the switch to the on position there is no warming up it will engage when I need it.  

Answer
John,

The overdrive on the Spitfire uses an electrical solenoid to move a mechanical lever that controls the flow of oil inside the o/d unit.  That solenoid is controlled by the switch on the shift lever.

It's not uncommon for the solenoids to fail, either electrically (burned out) or by becoming full of old oil/dirt and sticking.

With the ignition off there shouldn't be power to the overdrive switch circuit.  You can check by shutting the car off and using a voltmeter to check for voltage on the top fuse.  If voltage is present then it's possible a previous owner either accidentally or intentionally miswired the power feed from the igntion switch.

If you leave the switch on overnight, can you go from o/d to normal operation and back quickly in the morning?   Same question for when it's warmed up?

Another possibility is simply the battery is failing.  The starter motor takes a great amount of energy to start the engine.  Then it'll take some time for the alternator to get the voltage up to normal again.  By powering the solenoid before the starter there's a better chance of getting more power to the solenoid.


Cheers,

Jim