Triumph Repair: J type overdrive Triumph TR6, shifting into overdrive, pressure gauge

Question
TR6 is not shifting into overdrive. What are the correct steps to tract down the problem?

Answer
Hi Roger,
First confirm that the OD solenoid is activated when the OD switch is on and the gear lever is in 4th gear. If the oil level is correct and the solenoid is activated you need to run an oil pressure test. The plug is adjacent to the solenoid and you need a high pressure gauge that can go to 500 PSI. If the solenoid is not active, let me know and I will try to walk you through the electrical tests.

If it is active, you need to run the pressure tests with a gauge installed.

Run the rear wheels to 25 MPH in 4th gear and not in OD and the pressure should be about 20 PSI. Then activate the OD and the pressure should go to 430 to 460 PSI.
Howard