Ported or manifold vac for overdrive bypass vac switch?

[Liams55belvedere]

I have a vacuum kickdown solenoid installed on a 360la a500 overdrive combo, (got the car set up that way) and I'm wondering which vac port to run it to.

Here's the solenoid

The idea behind this (I'm told) is that during normal driving, it would go 1, 2, OD. But with this hooked up properly, when you floor it; it should go 1, 2, 3.

 

[MV8]

Manifold vacuum.That part of the circuit only provides power to the trans for OD and converter lock up. Are you using trans oil pressure, dash toggle, or throttle position switches to control these functions?

 

[TrailBeast]

I have a vacuum kickdown solenoid installed on a 360la a500 overdrive combo, (got the car set up that way) and I'm wondering which vac port to run it to.

Here's the solenoid
View attachment 1716293745
View attachment 1716293746

The idea behind this (I'm told) is that during normal driving, it would go 1, 2, OD. But with this hooked up properly, when you floor it; it should go 1, 2, 3.

Yup, manifold vacuum.
I set the vacuum switch on my A500 up, but found I really didn’t need it.
If I want out of lockup and/or OD I just turn it off.

The motor pulls good enough where I don’t need to take it out for passing.

 

[TrailBeast]

I have a vacuum kickdown solenoid installed on a 360la a500 overdrive combo, (got the car set up that way) and I'm wondering which vac port to run it to.

Here's the solenoid
View attachment 1716293745
View attachment 1716293746

The idea behind this (I'm told) is that during normal driving, it would go 1, 2, OD. But with this hooked up properly, when you floor it; it should go 1, 2, 3.

The way most set that up is so it disengages LU-OD or both when the vacuum gets low enough from more throttle.

Just a little FYI:
OD can only engage once the trans is in 3rd gear since 3rd gear fluid pressure is what engages OD.

Also note that if you are driving along in OD and lockup and manually downshift to 2nd,,,ZIIING!!!
You will be dropping lockup, OD and 3rd all at the same time, so don’t do that.

I would also be curious as to how the OD and LU shifts are made on yours.
Thanks

 

[Liams55belvedere]

The way most set that up is so it disengages LU-OD or both when the vacuum gets low enough from more throttle.

Just a little FYI:
OD can only engage once the trans is in 3rd gear since 3rd gear fluid pressure is what engages OD.

Also note that if you are driving along in OD and lockup and manually downshift to 2nd,,,ZIIING!!!
You will be dropping lockup, OD and 3rd all at the same time, so don’t do that.

I would also be curious as to how the OD and LU shifts are made on yours.
Thanks

Manually downshift to second?
I don't understand I guess.

I know very little about the transmission end of my setup honestly but what would I be looking for to answer your last question?

Also it might be important to note that there's two drive gears, O and D and when I got the car the guy said to just drive it in O?

 

[Liams55belvedere]

Manifold vacuum.That part of the circuit only provides power to the trans for OD and converter lock up. Are you using trans oil pressure, dash toggle, or throttle position switches to control these functions?

There is a kickdown cable but again I don't really know much about this so I don't know if that answers your question.

 

[TrailBeast]

There is a kickdown cable but again I don't really know much about this so I don't know if that answers your question.

What we are asking is what makes your OD and Lockup engage and disengage?

Is it simply switched, or is there some sort of automatic control over those two functions?

So far it kinda sounds like you don’t know yet.

 

[MV8]

Ditto. The vac switch by itself will not make the overdrive work. Are you saying you bought the car with this combo and it worked but you need to reconnect a hose to the vac switch? Look on the passenger side of the transmission for extra plumbing and two oil pressure switches and wiring or extra switches in the car to manually control it.

 

[TrailBeast]

Ditto. The vac switch by itself will not make the overdrive work. Are you saying you bought the car with this combo and it worked but you need to reconnect a hose to the vac switch? Look on the passenger side of the transmission for extra plumbing and two oil pressure switches and wiring or extra switches in the car to manually control it.

I really disliked the switches being directly on the trans exposed to who knows what.
I put an npt to compression union fitting on the governor port, and ran a section of cooler line up to the back of the intake and mounted my adjustable pressure switches next to the distributor so they can be easily accessed.

That said, anything connected to the governor port could be a hint as to what he has.

 

[Liams55belvedere]

Ditto. The vac switch by itself will not make the overdrive work. Are you saying you bought the car with this combo and it worked but you need to reconnect a hose to the vac switch? Look on the passenger side of the transmission for extra plumbing and two oil pressure switches and wiring or extra switches in the car to manually control it.

I bought the car with the combo and this whole time the switch was sitting there without a vac line connected. The overdrive has always worked though, and I will try to get a pic of it there are pressure switches on the side of the transmission

 

[Liams55belvedere]

Ditto. The vac switch by itself will not make the overdrive work. Are you saying you bought the car with this combo and it worked but you need to reconnect a hose to the vac switch? Look on the passenger side of the transmission for extra plumbing and two oil pressure switches and wiring or extra switches in the car to manually control it.

Okay I got some pics and it looks like they're marked so that's nice

would these switches be running off of vac pressure or the trans pressure?

 

[Liams55belvedere]

What we are asking is what makes your OD and Lockup engage and disengage?

Is it simply switched, or is there some sort of automatic control over those two functions?

So far it kinda sounds like you don’t know yet.

The od does kick in by itself

 

[MV8]

Okay I got some pics and it looks like they're marked so that's nice


View attachment 1716294241


View attachment 1716294242

would these switches be running off of vac pressure or the trans pressure?

They open and close the ground side of the overdrive and lockup based on trans pressure but the trans normally needs power through the vac switch. If wired correctly, the vacuum switch would not allow OD or lockup unless there is enough manifold vacuum to keep the vac switch closed (3 inches). The connections to the vac switch look correct but there should not be continuity between the connections (or test light power on both connections with the key on) without 3-7 inches or more vacuum applied to the port. The vac switch and attached micro switch may just need to be cleaned to get them working. The microswitch button is probably stuck and not designed to be exposed to the elements. Also, micrcoswitches are not normally rated to handle the number of amps that this circuit requires (14vdc with two, low ohm solenoids in parallel), so I don't expect a long life under the best conditons. Using a relay controlled by the vac microswitch would be best. The vac switch can be replaced with a spring plunger switch on the carb linkage but would still need a relay to be long lasting. If the microswitch is bad, they are dirt cheap.

The carb linkage kick down is an independent system and will kick down to second gear but leave OD and lock up engaged without the vac switch working.

 

[TrailBeast]

They open and close the ground side of the overdrive and lockup based on trans pressure but the trans normally needs power through the vac switch. If wired correctly, the vacuum switch would not allow OD or lockup unless there is enough manifold vacuum to keep the vac switch closed (3 inches). The connections to the vac switch look correct but there should not be continuity between the connections (or test light power on both connections with the key on) without 3-7 inches or more vacuum applied to the port. The vac switch and attached micro switch may just need to be cleaned to get them working. The microswitch button is probably stuck and not designed to be exposed to the elements.

The carb linkage kick down is an independent system and will kick down to second gear but leave OD and lock up engaged without the vac switch working.

OD can’t engage without being in 3rd, as OD gets its engagement fluid through the 3rd gear circuit.
So when kickdown drops 3rd it also drops OD.

 

[TrailBeast]

Okay I got some pics and it looks like they're marked so that's nice


View attachment 1716294241


View attachment 1716294242

would these switches be running off of vac pressure or the trans pressure?

Those work off the fluid pressure at the governor port.
Governor fluid pressure relates closely to the cars speed.
When your road speed reaches about 44 mph the switch that has 44 on it closes causing OD to engage.
The higher number switch does the same for lockup at about 52 mph.

It’s odd that neither one seems connected.

 

[Liams55belvedere]

Those work off the fluid pressure at the governor port.
Governor fluid pressure relates closely to the cars speed.
When your road speed reaches about 44 mph the switch that has 44 on it closes causing OD to engage.
The higher number switch does the same for lockup at about 52 mph.

It’s odd that neither one seems connected.

Should They have a wire running from the other tabs as well?

 

[MV8]

No, just the one tab per switch. Maybe Trailbeast didn't see that pic of the top of the switches.

So when it kicks down to 2nd, it also disconnects the lock up and over drive all at the same time. The vac switch controls coming out of overdrive and lock up at lighter throttle that is not enough to kick down to second but cutting power to the circuit.

 

[TrailBeast]

Okay I got some pics and it looks like they're marked so that's nice


View attachment 1716294241


View attachment 1716294242

would these switches be running off of vac pressure or the trans pressure?

Should They have a wire running from the other tabs as well?

As far as I know the switches are pass through, meaning they connect one terminal to the other making a connection to ground the solenoids inside the trans.
Mine do anyway, and besides being adjustable they work the same way.
The way yours are wired it seems one terminal can ground when activated.
Pretty sure those switches don’t do that, but you say OD activates, so this is a bit confusing to me.

No, just the one tab per switch. Maybe Trailbeast didn't see that pic of the top of the switches.

So when it kicks down to 2nd, it also disconnects the lock up and over drive all at the same time. The vac switch controls coming out of overdrive and lock up at lighter throttle that is not enough to kick down to second but cutting power to the circuit.

As I mentioned, the trans must first be in 3rd before OD can apply, but lockup can be made to apply in any gear and any speed.
(I tested this in second gear at 30mph) by manually grounding the lockup solenoid and lockup did engage.

My setup works entirely by ground switching with the trans having constant keyed power, so maybe that is where some of my confusion comes from.
My OD switch is set at 50mph.
When I hit 50 the adjustable switch closes grounding a relay only if the switch on the shifter base is in the Auto position.
That relay then grounds the OD solenoid in the trans activating OD.
When the switch on the shifter base is in the Off position the relay cannot activate OD.
All this also applies for lockup.
Here’s the picture again for easy reference.
I notice the switches shown are the older style kit that was offered with non adjustable pressure switches.
I used adjustable 35-70 lb. So I could set my own activation speeds.

This would be way more interesting and fun if we were all looking at and doing this in person.
I know I would like to see it all in person.

 

[MV8]

Many different ways to control most things and Trailbeast's wiring is different from yours in some ways. The OP switches ground the terminal through the plumbing to the trans case and are independent of each other. You could ground either solenoid and cause lockup or overdrive to engage at any speed and gear, since this bypasses the governor pressure in third gear that activates the OP switches. I'll draw a schematic.

 

[Liams55belvedere]

Many different ways to control most things and Trailbeast's wiring is different from yours in some ways. The OP switches ground the terminal through the plumbing to the trans case and are independent of each other. You could ground either solenoid and cause lockup or overdrive to engage at any speed and gear, since this bypasses the governor pressure in third gear that activates the OP switches. I'll draw a schematic.

View attachment 1716294499

Thanks for the schematic, what's the NO tab on the vac switch?
Before I started trying to set it up right it had the wire on that and not NC.

 

[MV8]

"NO" connection without the vacuum hose connected bypasses the switch function entirely. This could have been done because the microswitch failed or just out of confusion. Move the connection to NC, connect the vacuum hose and it should function properly or you can test it first with a test light. There should be power at both connections when the engine is idling AND power at only one connection key on, but not running.

"NO" is short for "Normally open". "Normal" is without the button being pressed on the microswitch but the vacuum portion presses the button with no vacuum applied, making "NO" closed and "NC" open. With at least 7 inches of vacuum applied, the vac spring is compressed enough that the microswitch button can go back to the actual normal position as if there were no vacuum switch.