Transmission / Overdrive: Help with logic on OD Solenoid Please

[mmagic]

Studying schematics of the BW overdrive system makes perfect sense to me until the Double Pole kick down switch is engaged.

The first step of the kick down process is to break the ground circuit to the relay/solenoid that alone should allow the system to drop out of OD. The second stage creates a new circuit to the solenoid that presumably forces it out of OD.

Why does the second phase draw its current from a distributor post ??

My curiosity is driven by the notion of a secondary kickdown mounted on shift or dash. Easy to break the circuit, phase one. But, phase 2 gets interesting.

[Mike]

The kick down switch contacts that you are asking about ground the ignition points, momentarily cutting power. This allows the overdrive to shift. It won't shift under load.
As you say, one side connects to the distributor. The other side goes to a terminal on the overdrive solenoid that is ground only when the solenoid is operated. As soon as the solenoid is released, contacts inside open removing the ground, and the engine goes back to full power.
When I wired overdrives for manual control, I didn't bother with that part. I just let up on the throttle when I was shifting the overdrive.
Are you aware that Stude used two ways to wire the control part of the circuit? One didn't use a relay.
Mike M.

[mmagic]

Thanks... I'll study from that perspective.

The only schematics I have found use the relay and I have no problem using/understanding a relay. My rewire includes 8 or 9 already.

[BobPalma]

Randy Rundle's Borg-Warner Overdrive book, advertised every month in Turning Wheels, is a fine reference. It has excellent diagrams for understanding, diagnosing, and repairing overdrive problems.

He sells it through his enterprise, Fifth Avenue Auto Parts in Clay Center Kansas. Highly recommended. BP

[PackardV8]

Be aware some of the overdrive manuals/pamphlets sold only deal with the older relay/2-wire solenoids. They don't show the newer no-relay/3-wire solenoids.

Also, Studebaker used two different kickdown switches. The make connections differently internally. One goes with the relay/2-wire and one goes with the 3-wire. Make certain one is consulting the correct Shop Manual for the system being installed.

jack vines

[Mike]

There are a few variations shown in the diagrams at: https://www.studebakerparts.com/stud...ediagrams.html . Solenoids with two or three terminals and governors with one or two are shown. It's useful to see how they work, in case you have to use an unfamiliar solenoid or governor.
The fuse on the kick down switch is badly drawn on some. It's only there if a relay isn't used; and connects only to the side that controls the solenoid. The side that grounds the points is the same.
Mike M.

[mmagic]

I have the 2 wire solenoid and kickdown and am wiring my own relay to support it.

Without applying serious thought, if I should elect a secondary kickdown driven by a momentary contact (NOC), it looks like I may need two relays to make it execute like the current kickdown... one to break the ground to relay and one to ground out the coil.... for thought as this can be added later.

[Mike]

Yes. The kick down switch is really two independent switches.
The normally open side grounds the ignition points, when the throttle is floored; allowing the overdrive to shift.
The normally closed side breaks the control path to the solenoid.
All that's needed to manually control the OD, is a switch or relay in the control lead to terminal "8" of the solenoid. If it's a three wire solenoid,
terminal "4" should be hard wired to ground.
Mike M.

[mmagic]

Ordered a DPDT relay today. Should be able to use one side of the kickdown and as many momentary contact switches as I want... need to think through the diagram.

[studeluvr]

This is great since I'm in the process of wiring the OD on the 40 a 2 wire system. I wondered why the wire from the distributor went to the solenoid. Actually I think my car had it going from the coil to the solenoid would it serve the same purpose? I've never liked flooring it to kick in the OD so I've always wired in a toggle switch and let off of the throttle when engaging the OD. This forum has great stuff.