[TR] TR4 overdrive

[Randall]

Things I would check first;

Clean the hole in the operating valve stem. 

Check how far the ball in the valve moves (IMO should be around .030" minimum, but some like it smaller. Under .020 can cause erratic operation.) The adjustment hole in the side is not always accurate, and the adjustment can sometimes slip.

Hook up a voltmeter/DMM to the relay output, to be sure you're getting full 12v while driving. I have had them fail such that they do OK without pressure in the OD.

Take a test ride with the tunnel out, and try pushing directly on the setting lever. If that makes the OD engage reliably, the problem is in the outside (perhaps dirty contacts in the solenoid).

Not all A types are identical, but they all have accumulators. TR2 through early TR6 and early Stag all had A types (when they had OD), but other Triumphs had D types or J types (which did not have accumulators).
-- Randall
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