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Th400 kickdown switch options.

broncoman6524

broncoman6524

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ok ive got a k5 that had a 700r and it died, took it to a shop and decided htat for a whopping $200 more i can get a brand new 400 instead of rebuild the 700 did that. Now this is about 6 months later, i am not ever remembering the trans EVER having any form of kickdown. I was looking around today and inspecting the trans. i know the little spade is for the kickdown there was nothign attached. IS there any possibility that a vacuum siwtch mounted inline of the vacuum to the modulator could do the kickdown? bc there is a vacuum switch that after ive checked it is not openign or closing regardless of vacuum.

In other words can a vacuum switch be used to control kickdown to the modulator or is it only electric? and this switch WAs for my lock up converter...

Ill try and explain how its set upa nd ill get pictures tomorow. Behind the carb, theres a vacuum port, on hose going to a T one line from manifold in, one to modulator, and one to this switch. On the other side of the switch is a 2 spaded Female plugin.

Anybody got a clue as the the 1st question or wtf this swithc is? i went to napa and discount and nobody could give me a straight answer, they enven ran the number.

thanks guys:bow: i REALLY wanna have the power of kickdown...w/.o spending the $50 for the B&M kit.:haha:

the switch resembles this one except with 2 female connectors not male.
VacuumWire.jpg
 
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You need to apply 12 volts to the electrical connection to make it kickdown.

Depending upon the year of your k5, the bracket bolted to your gas pedal pivot may have a place to attach a factory slide switch to it. Then series an IGN circuit through the switch to the tranny plug. Done.
 
I suppose if you had the right switch you could use vacuum as the kickdown, but it would probably not be as positive as the pedal method GM used.

Without the right switch vacuum settings, you might get it to kickdown when you need to speed up 3MPH while going 60. :)

The torque converter switches IIRC actually did take a fair bit of pedal to get to "unlock".
 
when you say slide switch...what do you mean exactly? like a push button thingy mounted as where teh pedal would be at WOT? and oncei put this switch there ifi floor it and its already in 2nd it will still shift to 3rd but much later correct? bc i can get it to not shift past 2200...unless i shift it manually. which sux since about 1600+ is my powerrange .lol
 
he means a on off switch up on the top of the gas pedal
go to a pick a part and get on from an old 1 ton before 1990
hook up keyed ign power to on side and the other to the spade terminal
you can also get an active part throttle kickdown using the transgo basic shift kit and installing the active spring and then spending time setting the modulator
 
I believe the Jeeps that had TH400's used them as well. I recall someone mentioning that application.

ANY GM car OR truck with a TH400 is going to have some sort of kickdown, you might look at some Cadillacs from the 70's in a wrecking yard, see if the pedal piece isn't identical, or close enough to be made to work.

Or just buy the right piece. :)
 
Factory the best way...

Yes,Dorian has the right idea..why mickey mouse something when the "right" parts are sitting in the junkyard?..I do think the Caddy's and other large GM cars used similar switches,but they might not fit a truck..

Now that I think about it,some years of Buicks and Caddy's had the switch mounted on the carb linkage,and would engage passing gear as you floored the throttle..it would not be too hard to jerry-rig something similar,but they used the TH400 in many later trucks,even with 4.3 V-6's,so its not like there are none around anymore,why bother screwing around?..I'd go visit the boneyard,I bet you'll find one in another truck...:crazy:
 
Kee-rect. Caddies used a carb-mounted switch. That would be easier to set up in a vehicle that was never equipped with a TH400 but I'm a big fan of using the right parts in the right place, so the pedal-mounted switch would be the way to go in this case.
 
gotcha. from what ive seen (aftermarket) the 2 kits for this type of stuff is like yall have said a switch that mounts onthe manifold and then a chain is hooked up to the linkage blahblahblah. i guess ill check the yards this week and try to find one. thanks guys
 
TH400 kickdown switch

I know this is an old thread, but I was doing a search and saw it, and then I found more information I thought my be helpful here since everyone seems to be going to junkyards to try and find one of these switches. You can still buy the switch brand new from the GM dealer, it bolts right into the bracket on the gas pedal of our trucks, and it's about $23. GM Part # 1242101. It has two spade terminals, just connect one side to the 12V ignition power, and the other side to the kickdown terminal on the TH400 trans as these guys stated before.
 
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