Re: Continuing on the Overdrive

Posted by Jim Kavanagh On 2009/9/3 12:20:58

The source of the buzzing is a mystery. It is quite quiet, and the car also is quite quiet. With the windows up or down, I can not discern the direction of the noise from inside the cab. And I can not tell whether it is electrical or mechanical.
The mechanic who replaced the solenoid to get the OD working felt it was "somewhere inside the overdrive (and you don't want to take that apart)". At that time, it occurred only intermittently. It now occurs whenever a shift into OD is done.
The only time it occurs is when the solenoid is activated, pushing the pawl onto the balk ring, which has not yet rotated to allow engagement. Once engaged, no noise, and everything works as it should.
I am leaning toward it being electrical because the mechanic was right, I don't want to take the OD apart.
I think I could get much closer to the answer by putting the car on jackstands and performing the shift to OD. From underneath, I could probably tell if it was from the OD unit or the solenoid.
But, I haven't been immortal since my twenties, so I am not anxious to do this - maybe as a last resort.
I am thinking about this: Disconnect all four leads to the solenoid and the OD lead to the governor. Run a tap switch from the governor (or maybe just ground?) directly to the solenoid terminal 4. Get up to about 20 MPH and hit the switch. Since I wouldn't have terminal 3 powered, I would not actually allow the shift. If I hear the noise, then it is either the solenoid or something in the overdrove mechanics, if I don't, then it must be electric.
I seems to me that there should be no likely damage to the system by doing this, I think I am just duplicating the sequence after the governor closes the points and before I release the accelerator to shift into OD. I don't think there should be any issues of overloading the solenoid or the governor, as long as I do the engagement for only a short while.