Hey all, I'm trying to figure out how to move forward with a potentially faulty stator solenoid in the TH425 in my '66 Toronado.

The multifunction detent/stator switch is correctly passing 12v to the detent solenoid because I am getting transmission kickdown upon WOT. However, last time I checked with engine off, I don't believe I heard the stator solenoid clicking. And I don't seem to feel the "half downshift" so to speak, when I get to approx. two-thirds throttle. I still need to run a jumper wire directly to the stator solenoid to see if the switch is at fault, so I cannot yet rule out the switch being the problem.

I've also ohmed both solenoids through the wire that attaches to the switch. The detent solenoid reads 11 ohms and the stator solenoid reads 20 ohms. Are these different values correct? And could the stator solenoid still be malfunctioning even though there is no short or open?

My big question comes down to the solenoid itself. The factory parts catalog lists two different part numbers for the detent and the stator solenoid. The stator solenoid is not available new, but the detent solenoid is. I've heard people say that the only difference between the two is wire length to reach the case connector in the side of the transmission, but I've also heard people say that they are fundamentally different due to the stator solenoid being energized constantly at idle, so it is a more robust solenoid (hence the higher resistance?) I can find NOS stator solenoids, but I would like to know first if I can buy a brand new detent solenoid, extend the wire length, and use it as a stator solenoid, or if I should purchase a NOS stator solenoid.

Thank you all for your input!

 

Oh boy you're right on the money noticing the difference between those two solenoids. It's a great question and you're right to be thinking ahead on this. Here's what my AI Agent that's specially trained on the 1966 Toronado has to say........

I kid. I kid. It's only a matter of time before he shows up on here isn't it?

 

Hahaha you are not wrong there. I find AI useful to perform calculations/organize information that I already have empirical knowledge of, but to rely on it for stuff like this is a bit far-fetched. Some things require human experience. AI has its place, but I worry how it'll be used going forward, especially by bad actors.

 

If AI had scanned the 1966 Oldsmobile Chassis service manual it might prove to be of some help.
But, doing it yourself is probably easier than finding an enlightened AI.
Original 1966 OLDSMOBILE CHASSIS SERVICE MANUAL! | eBay

 

I have a copy of the service manual, factory assembly manual, two different parts catalogs, and fisher body manual, so I'm not hurting for references. I've found that none of the factory literature delve into the technical details of the solenoids; they only list on-car test procedures and replacement procedures. Although, for the solenoids specifically, there are no specific replacement procedures, it just shows them in the transmission teardown and rebuild procedures. I guess I should clarify that I have the knowledge on diagnosis, I'm just more concerned with, if the solenoid has failed, having to cross my fingers on a NOS solenoid that is already over 50 years old, or if I can get away with using a new detent solenoid to use in place of the stator solenoid, and whether or not they are electrically/mechanically different parts. And if a solenoid can be bad even if it ohms out. I guess it also helps me to bounce things around a little with others' help, that way I know I am doing things at least somewhat correctly haha.

 

Just start on the easy stuff first. You should have power down at the connector on the side of the transmission when the ignition switch is on and the throttle is set in the idle position. So grab a 12V test light, even a bulb or something would do, and test for power at the upper (horizontal pin). No power = no stator control.

Those solenoids are built solid and tough as nails. I'd be surprised if your problem isn't elsewhere.

 

I haven't used a test light yet, but when I backprobe the connector on the switch (on the harness that goes down to the solenoids), I do get 12v output from the switch at idle. Someone brought up somewhere that badly corroded/oxidized switch internals can cause a voltage drop when the solenoid energizes due to it pulling a load through the high resistance that the switch is causing. My line of thinking, which I still need to do, is to bypass the switch and directly provide 12v to the solenoid to at least listen for a click to see if I need to take the switch apart and clean it.

And yes, my fear is that it is a problem either with the torque converter or a passage in the transmission.

Also, can the solenoid be gummed up and not function properly even if it is clicking/ohming out? I know these questions will be answered when I pull the pan to look at things, I guess I'm just looking for some insight before I get to that.

 

Here's my kickdown/stator switch when I disassembled it ('66 Toro). Look at those contacts. I would see 12V on a multimeter but with a test light it's a different story. You need to check the wiring right at the transmission connector in a loaded condition (i.e, an incandescent test light) to make sure the wiring is good and that the switch is rigged correctly.

 

Wonderful photos, thank you so much!