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Previous owner did something to my kickdown switch -any guesses?
1970 442 with a 1967 TH400 transmission. The attached pic shows a plug under the hood one green wire leads to the transmission & the other goes into the wiring harness (I think it goes to the switch on the gas pedal but haven't followed it for sure). So what's the green thing with the wire that connects to both sides on this plug? There are NO plugs anywhere under the hood that this would plug into. I'm speculating that this was a way to bypass the firewall plug & makee the kickdown switch work on a 1967 Trans? The kickdown is not currently working.
That plugs onto the TCS (transmission controlled spark solenoid) that mounts on the manifold. If the transmission doesn't have the second tab at the kickdown tab, then don't worry about it.
The kickdown on the T400 is obviously electric so it requires a switch of some sort. In addition, a 67 T400 for an Abody was a switch pitch (variable vane) torque convertor, so would have required another switch in conjunction to operate correctly. You need to see which T400 you have in your car. Work from the transmission and follow the wires to the source and see where the switch/s are.
Just to let you know the Switch Pitch will work fine not being connected but will always remain in low stall. You can verify what you have by looking at the connector in the case on the drivers side of the transmission. The connector should have two pins on it. One horizontal and the other vertical. The top one is for the Switch Pitch and the bottom for the down shift. All they need is 12v to operate. How you hook that up is up to you.
Your other question about that connector and the wire between both terminals is probably a diode to prevent back feed of electricity between the circuits. Just my guess.
This is one way to wire the S/P but there are many possibilities. Bruce Roe probably has the best kit out there. If memory serves me right the connector in this pic is upside down. I think the horizontal is on top.
Thanks guys - that's helpful. That diagram shows a toggle switch - why would that be needed? To manually turn the kickdown off & on? It's interesting that I have also found an after market toggle switch stuffed up under the dash that is connected somewhere up around the heater control switch wiring harness. I wonder if the PO did this conversion when they swapped in the '67 TH400, like in the wiring diagram you show & left it up under the dash? I'll work on tracing that while I'm at it.
The toggle switch in the diagram is to engage the low-stall mode of the converter.
I don't know what the toggle switch in your car is for, though.
Honestly, I must point out that I don't know why the brake light circuit is being used in that diagram to engage the low-stall mode, and I would point out that in that diagram, the toggle switch would also turn on the brake lights.
Well then I guess I WON'T use the brake circuit as a 12V source! Why would you manually engage the low-stall mode? And am I thinking right that I can ignore the TCS/switch pitch and just focus on getting the kickdown switch working?
TCS and switch-pitch are two different things, and never existed in the same place at the same time.
TCS is a cleverly designed way of robbing both fuel economy and performance, and involves only activating the vacuum advance when the vehicle is in top gear. To achieve this, GM created a terminal on the transmission that grounds when it is in 3rd, to turn the TCS off.
Switch-pitch converters can switch between low- and high-stall modes, thus essentially creating an artificial low gear. When the switch-pitch terminal on the transmission is energized, the converter goes into low-stall mode for takeoff from a standing stop or for acceleration.
As originally installed, switch-pitch cars had a round switch as part of the throttle linkage at the firewall, which energized the switch-pitch terminal at the lowest and highest throttle positions, as well as energizing the kickdown terminal at full throttle.
In order to get the switch-pitch feature to operate properly, you need to do the same thing.
Thank You! I get the old & new TCS vs. switch pitch & my car was made different than the trans, but this is the best explanation of why the difference matters. I'll take this info & run with it.
Yes, Joe, we did cover it, but I'm slowly getting schooled on transmissions. You explained well that the transmissions were different & that one had a TCS & one had a switch pitch, but I didn't understand what the two did differently & why it mattered, whether or not I should pursue getting them hooked up, etc. Really I'm just trying to figure out how much to attempt to get the kickdown switch working, & whether or not I should be concerned with the TCS/switch pitch. I apologize if I'm wasting your time - just trying to become less ignorant on this particular subject.
If you really aren't quite getting this stuff, I would recommend connecting a toggle switch from a +12V source to each of the transmission terminals, and switching each one while you drive to see what it does. That will also serve to test whether the parts are working.
If you really aren't quite getting this stuff, I would recommend connecting a toggle switch from a +12V source to each of the transmission terminals, and switching each one while you drive to see what it does. That will also serve to test whether the parts are working.
- Eric
That's a great idea - I'll give it a try, & maybe this will resolve my ignorance!
Although I don't remember where I got that picture I think what was going on is they were trying to duplicate the factory switch without having the factory switch. The factory switch put the converter in high stall while at idle to stop 'creep' say at a stop light. Having the brake switch activate it does the same thing essentially but without the delay built into the factory unit. The toggle switch is just there to disengage the circuit if you wanted to. This would result in low stall all the time.
June 6th, 2016, 05:54 PM
