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09-30-2024, 11:28 PM
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#1 |
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Registered User
Join Date: Aug 2020
Location: Grants Pass Or
Posts: 39
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Turbo 400 kick down question
I've found a wire attached to the trans and assume it's related to kick-down. Is it triggered by 12V and from where? Bob
Last edited by Rickysnickers; 10-01-2024 at 08:59 AM. |
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09-30-2024, 11:52 PM
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#2 |
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Registered User
 
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,633
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Re: Turbo 400 kick down question
Best idea is to check the wiring diagram for the donor rig. Or search out Turbo kick down switch or passing gear switch.
__________________
Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around. |
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10-01-2024, 09:20 AM
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#3 |
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Registered User
Join Date: Nov 2010
Location: calgary alberta
Posts: 8,185
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Re: Turbo 400 kick down question
turbo 400 has an electric switch activated by the accel pedal inside the cab normally. it is 12v fused supply from a "hot with key in run" fuse box connection. just google the topic for a few images of what the switch normally looked like and what the aftermarket hotrod suppliers are supplying.
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10-01-2024, 08:24 PM
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#4 |
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Registered User
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,633
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Re: Turbo 400 kick down question
The switch can be inside the cab connected to the gas pedal or on the throttle linkage at the carb.
https://www.ebay.com/itm/12598909698...G090XKZ6B0HAFJ https://www.ebay.com/itm/13467992884...YaAizlEALw_wcB The switch for the Edelbrock carb would probably be the simplest to hook up on a truck. The other switch goes on the throttle pedal assembly and you pretty well have to use the whole assembly. The style in the photo was used on Oldsmobiles a lot but you have to have the lever on the carb designed for it.
__________________
Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around. Last edited by mr48chev; 10-01-2024 at 08:33 PM. |
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10-01-2024, 10:31 PM
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#5 |
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Registered User
Join Date: Nov 2010
Location: calgary alberta
Posts: 8,185
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Re: Turbo 400 kick down question
It's a simple switch. There are lots of variations you could use. Back in the day as a heavy duty mechanic Mack trucks used a simple micro switch on the linkage in order to operate the Jake brake. It had a built in diode to stop reverse power flow from energy developed when the magnetic fields collapsed in the Jake actuator solenoids
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10-01-2024, 10:39 PM
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#6 |
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Registered User
Join Date: Nov 2010
Location: calgary alberta
Posts: 8,185
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Re: Turbo 400 kick down question
this is what they looked like just for reference. a switch similar to this could be easily placed on the throttle linkage so that the kickdown would operate properly. not necessarily this switch but you get the idea
https://www.ebay.com/p/2099396414 here is a thread that discusses the kickdown switches. it is interesting that some are operated by a chain that lookslike a tub drain plug chain. whatever works and has longevity I guess. i seem to remember Ford had a similar set up https://67-72chevytrucks.com/vboard/...d.php?t=679916 |
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10-01-2024, 11:31 PM
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#7 |
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Registered User
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,633
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Re: Turbo 400 kick down question
Ebay sellers are nuts on used OEM Chevy kick down switches. Only for the restorer shooting for a 100 point car.
Personally I'd look into the 30 something buck micro switch. I may have to get one of those for my 71 GMC with the Cad 500 in it. I want to get it running and driving before winter.
__________________
Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around. |
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10-02-2024, 08:54 AM
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#8 |
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Registered User
Join Date: Mar 2012
Location: Lakes Region NH
Posts: 3,189
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Re: Turbo 400 kick down question
With a BBC installed, it seems like someone must have replaced the original gas pedal with one from another vehicle? Here's a square body truck gas pedal with a THM 400 kickdown switch. The switch is near the top of the picture. It's the tan parts.
 This one is for sale for $25 from a guy in PA. https://www.hillbillywizard.com/cucv...bly-for-th400/ If you use a microswitch or other low current device you might want to consider using a relay to go with it. If you have a column mounted dimmer switch you could use the old floor switch to control kickdown. I have done this and it can be nice to force downshift at light throttle for a little help accelerating or going uphill. Loving the heater bypass hose. 
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