Re: R9 Overdrive

Posted by HH56 On 2014/2/20 10:06:34

When you said it suddenly dropped out, that does sound electrical. If it acts as if the OD knob is pulled out, does the green light come on when you are starting out and reach the engagement speed? If not then most likely electrical and Kev has listed the things to check.

If power is getting to the system and fuse & reverse safety switch are good, some known but unusual and not commonly looked at electrical failure points have been:

The governor ground. Corrosion or looseness of a small screw holding the case and rear cover. The one in question is located at the metal tab on cover & is the one which feeds ground to the governor contacts.

The lockout switch. The switch actuator plunger is soft bakelite and the continual sliding against the lockout rod can wear the plunger down at the end. If that happened and it was worn enough, vibration could suddenly make the lockout switch no longer have contact when knob is pushed in.

You have already addressed the kickdown switch once but worth a look again anyway.

The relay itself. Make sure the side with double contacts is pulling in and the lower set of contacts have not burned. Those lower ones are the contacts that power the solenoid.

The loom. Your car may have a late one piece harness or had the problem looked at early on. If not, early harnesses had problems with the inline connectors between the main loom and the short 3 ft length connecting to transmission. The connectors were eliminated in later looms or removed in the field per service bulletin. If you still have them in your car, corrosion and sudden or intermittent loss of connection was a problem.

If the green light does come on but no engagement, then solenoid pull in or mechanical bind would be suspect. There is a set of contacts in the solenoid -- part of the pull in coil circuit that need periodic servicing. If those have failed, the solenoid cannot pull in and would explain the no engagement problem but would not have been the cause of the sudden dropout.

You can narrow it down a bit by use of a jumper. With ign on, engine off, trans in neutral, momentarily short terminal 5 at the relay to ground. That will bypass all the switches and most wiring. If power is there and relay is good, You should hear the relay activate and the solenoid should try to come in and will give a good clunk.