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MG MGB Technical - overdrive asleep

The overdrive on my 1972BGT won't engage. I have changed the gearbox oil (20w50), fitted a new solenoid and checked the power supply and switches. Also renewed the O/d filter.
Any ideas please.
wil wilkinson

Check the inhibitor switch (when in third or forth pull the gear stick towards you if the overdrive engages thats the problem)
K Harris

Thanks K.Harris I willtry your advice
W.J Wilkinson

I have experienced a similar problem on my UK made 1971 B, it turned out to be the dash switch. They are apparently a problem and it is a simple fix. The switches are readily available form Moss or any toggle switch will do if you do want to stay "original"
Good luck Ian
I Denton

I Denton

Thanks for your comment

Wil Wilkinson
W.J Wilkinson

You can check for voltage easy enough which will reveal problems with the switches and connections, but that still doesn't tell you whether current is actually flowing through the coil. You could turn the dash switch off, engage 3rd or 4th then measure the resistance to earth at the connector in the yellow and yellow/red wires in the mass where the main harness joins the gearbox harness, and should see about 15 ohms. Or part that connector and insert an ammeter and you should see about 800mA with the ignition and manual switches on and the gearox in 3rd or 4th. If you see those, then the problem is mechanical or hydraulic inside the OD. If this suddenly started happening without having done anything to the OD after working normally, it could be the relief valve, or maybe it was the solenoid, did you find and replace the little ball-bearing on the end of the solenoid shaft? Without that it won't work.
Paul Hunt

Hi Paul

Thanks for te info

Wil
W.J Wilkinson

This thread was discussed between 14/07/2009 and 17/07/2009

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