Kickdown system education needed

[PbFut]

After 50+ years of hot rodding, this is my first automatic transmission I’ve owned. After doing some research I am not 100% sure on a few details of the TH350 kickdown system. As I understand it, there are 2 switches, so to speak, that will drop the transmission down from drive to 2nd. One is the vacuum module that, as I understand, limits the line pressure in the transmission to delay shifting further up the RPM range or down shifting when a low vacuum state is achieved under heavy engine load. I am guessing there is some sort of mechanical weight governor as well to work in conjunction with the vacuum module. The kickdown cable is a little less clear to me. Does the cable modify the vacuum signal which in turn affects line pressure and ultimately shifting? Or, is there a second valve in the pressure line adjusted by the kickdown cable directly. Is this kickdown cable system variable or like an on off switch closing a valve at the last bit of throttle travel?
The modifications I am currently in the middle of will need to eliminate the kickdown cable. Can I use a micro switch to trigger a solenoid activated vacuum valve to close the vacuum line to the module and get the same down shift result? Is this how a TH400 works, given there is an electrical switch involved with that transmission?

[Rust_never_sleeps]

TH350 actuates a valve directly.
IIRC, 400 is also valved, but a switch on the carb triggers a solenoid to open it https://www.onallcylinders.com/2014/...like-3-speeds/

I Stole this snippet from Ken Ruggles' book, (which has a whole section on performance mods, but I ain't never done that):

[PbFut]

got it. Thanks Rust. So now I need to engineer a solenoid setup that will pull the cable at WOT. Anyone know of a kit?

[Accelo]

The THM350 only requires a cable and bracket to be functional. Nothing electrical.
You can run without it but it will lack the crisp down-shift it will have with it working.

The 700R4/4L60 has a TV cable and has to have it connected and functioning or it will immediately trash the transmission.

The 700R4/4L60 has a TV cable looks like and connected the same as the kick-down cable but the function is completely different.

Unless. by chance, you have a THM350C with the lock-up converter and you want that to function. It is electrically powered.

[mrein3]

Just about any turbo 350 kickdown cable assembly should work.

When I converted my 4x4 from a 3-on-the-tree manual to a th350, I used the kickdown cable off of a 1971 Monte Carlo.

When you think about it, it is likely that all kickdown cables are the same. The transmission in relation to the engine is in the same position distance wise from the carb in all applications.

[Accelo]

All kick-down cables are not the same.
The early 1969 and 1970s C10s took a different cable and bracket.

I have attached a picture of the later style cable and the 1969 style kd cable bracket.

They adjust quite differently.
However, the statement is typically true for most cables.
Mostly they differ in the carburetor attachment style.
Unless your truck is completely stock it will likely have to be fabricated anyway.

[Rust_never_sleeps]

IIUC, what OP needs is an electronic substitute for the physical cable
TH400 type switch-->solenoid adapted to the TH350