Transmission / Overdrive: Powering overdrive solenoid after 12V conversion?

[Tipjar]

The previous owner of my '50 Commander convertible (17A body style) with overdrive had a shop do a 12V conversion for the motor, lights, and dash gauges but not accessories like the clock, radio, and convertible top motor. I've figured out with a wire tracer that one unattached black wire under the hood goes to a relay that deals exclusively with the overdrive solenoid. The loose black wire is the power source to the relay/overdrive solenoid and presumably used to be attached to the source terminal of the starter solenoid based on its length and position. (The starter was updated with the 12V conversion and it's solenoid only has two terminals, one each for the battery and ignition, there's no separate output terminal like images in the parts catalogue show on the original. Also, the overdrive has been functioning mostly fine without power to it's own solenoid; it can be temperamental after climbing a hill though.)

The fitting on the end of the unattached black wire is not a large enough diameter to fit around the source terminal on the updated the starter solenoid, but from what I can see in the parts catalog it looks like it may have fit the source terminal on the original starter's solenoid. It doesn't take much effort to change the fitting on the end of the wire, which has me questioning why the shop that did the conversion didn't bother. It could be that the budget was used up and they didn't want to follow up. Or maybe not.

My questions are:
1) Am I correct the relay for the overdrive solenoid can get its power from the source terminal on the starter solenoid (which is simply serving as a passive junction)?

2) Is it possible the overdrive solenoid is designed for 6V and that's why it was left alone after the 12V conversion? If so, can I just add an inline 12V-to-6V resistor between the power source and relay? If so how many amps would you recommend it be rated (3A, 6A)?

3) If the original 6V system was positive ground do I have to make changes to the wires on the relay and overdrive solenoid for the 12V negative ground system?

4) Why does the overdrive even have a solenoid if it has been functioning without any power to it?

[StudeRich]

(2) Yes, the Shop realized that if they powered up the 6 Volt Solenoid with 12 Volts, THAT would not be a good thing!

The Overdrive Governor, Reverse Lockout Switch and the Kickdown Switch are not Voltage sensitive, but the Solenoid and Relay ARE.

(3) The electrical components only need Power vs Ground, so when you switched the Coil Wires and the Battery Cables, the Positive to Negative Ground conversion was done, but not so much the 6 Volts to 12.

[RadioRoy]

The relay and the solenoid are not sensitive about polarity. The ARE sensitive to voltage, so they need to be replaced with 12 volt items.

You cannot add a dropping resistor to the solenoid, as it has two different windings (one pull in and one hold in).

[Ross]

Am quite intrigued that your overdrive works with no power to the solenoid. You mean, at about 30 you lift your foot off the gas and it shifts up and then shifts down again when you get below twenty?? You don't just mean that it freewheels? About the only way it could be working without power is if a prewar overdrive that upshifted by means of flyweights inside the case had been substituted for the later unit. The solenoid on that unit would be only about oh, 1.5 inches long and was only used for kickdown.

[gordr]

I think it's safe to assume that Tipjar has never driven a car with properly-working overdrive. That's not a slam; just a fact of life. You have to be of a certain age to even have had an opportunity to drive an overdrive-equipped car.

Agree that step-down resistors will not work for the overdrive solenoid or relay, but 12 volt versions of those parts do exist, and can be bought. You can use a 12 volt 2-terminal solenoid and a 12 volt relay, or get a 12 volt 3-terminal solenoid, and dispense with the relay, but a new wire harness must be made.

[Tipjar]

Am quite intrigued that your overdrive works with no power to the solenoid. You mean, at about 30 you lift your foot off the gas and it shifts up and then shifts down again when you get below twenty?? You don't just mean that it freewheels? About the only way it could be working without power is if a prewar overdrive that upshifted by means of flyweights inside the case had been substituted for the later unit. The solenoid on that unit would be only about oh, 1.5 inches long and was only used for kickdown.

When I lift my foot off the half depressed accelerator in third gear something changes that feels the same as overdrive in any other car I've driven. The car glides easier, deceleration is less tied to rpms, and pick up of the transmission is slightly more sluggish. Conversely, after I do a rapid kick down of the accelerator something feels as though it disengages and the relationship between the engine and transmission becomes tighter and more responsive and the car doesn't glide as easily....However, that solenoid must serve a purpose so I'd be interested in feeling the difference once the parts are updated.

[Tipjar]

I think it's safe to assume that Tipjar has never driven a car with properly-working overdrive. That's not a slam; just a fact of life. You have to be of a certain age to even have had an opportunity to drive an overdrive-equipped car.

Agree that step-down resistors will not work for the overdrive solenoid or relay, but 12 volt versions of those parts do exist, and can be bought. You can use a 12 volt 2-terminal solenoid and a 12 volt relay, or get a 12 volt 3-terminal solenoid, and dispense with the relay, but a new wire harness must be made.

I've had plenty of cars with overdrive, stick and automatic, but never pre-1970. Thank you for the parts information.

[gordr]

I've had plenty of cars with overdrive, stick and automatic, but never pre-1970. Thank you for the parts information.

Sounds like you may not have driven a car with the Borg-Warner overdrive, then. Your description in your previous post seems to indicate that you are experiencing "free wheeling", which is the action of the over-running clutch in the overdrive. It allows the engine to drive the car, but the car cannot drive the engine on deceleration. You know, if the overdrive is indeed working properly, maybe the the shop that did the conversion did install a 3-terminal solenoid, and wired it correctly, but simply disconnected the relay, and failed to remove it.

I'd recommend that you try to contact one of the members from the San Diego are who is familiar with driving overdrive-equipped Studebakers, and ask that person to test-drive your car. Does the car behave differently when the lockout knob is pulled out.

[StudeRich]

Exactly!
When you drive an Overdrive Car with the O.D. handle "IN" for in Overdrive, but the Solenoid is not working, above Approx. 32 MPH it FREEWHEELS, so when you have released the Gas and then get back into it, it hesitates and takes off harshly back into Direct with a Lurch and more RPM. This is NOT Overdrive.

[Corbinstein0]

My 6V Solenoid works just fine on 12V. Been that way for 20 years. How much longer is anyone's guess, tho.

[Tipjar]

My 6V Solenoid works just fine on 12V. Been that way for 20 years. How much longer is anyone's guess, tho.

Does that mean you still use the 6V relay as well?

[Tipjar]

Does the car behave differently when the lockout knob is pulled out.

I haven't tried that yet because I wasn't sure what kind of operation is allowable with it pulled out and I didn't want to risk damaging anything. And I haven't met with local club members yet (fortunately there's one in my area). I'll try it soon though. Other parts are currently out for reconditioning.

[StudeRich]

It is perfectly OK to Pull the lever Out to get Deceleration and save the Brakes at Below 35 MPH or so, and from any speed slowing down with compression helping you.

BUT, DO NOT do that with the Car MOVING, it will damage the O.D. !

After you get the Overdrive working properly and used to driving it, we can explain How that is done moving, but it's too early to worry about that at this time.

[Corbinstein0]

Does that mean you still use the 6V relay as well?

nope. relay AWOL

[Tipjar]

Thank you all for pointing me in the right direction. I see prices for the Borg Warner R10 12V solenoid ($385) and relay ($130) may partially explain why the previous owner never got around to it. And this brief article on Hemmings mentions the longer shaft solenoid on convertible models can be very difficult to find. I haven't removed mine yet to verify. I may have lucked out with Eurton Electric in L.A. who specializes in rebuilding anything with a coil and are familiar with converting to 12V, if so their estimate is $250-$325.

Key passages from the article:

"Many collector-car enthusiasts today, who convert their car to the more efficient 12-volt systems, also have a problem converting the overdrive because it is not as simple as adding a voltage reducer to a 6-volt unit. The original windings in a 6-volt overdrive solenoid were made in two different sizes, a larger primary winding to activate the solenoid and smaller secondary windings to keep the solenoid engaged once it has been activated. A standard voltage reducer will not work in these applications."

"The exceptions to these interchanges apply to convertibles, pickups and station wagons. Units for those types of vehicle are extremely difficult to find as they have a longer engagement shaft than a conventional hardtop or sedan unit and do not interchange."