Thread: TH-400 kickdown switch ??

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I just installed my tranny after getting a mild shift kit put in by the local shop. After install, I was driving it around and noticed some white smoke trailing me. I pulled over to find tranny fluid dripping on the headers from the TOP of the engine...... I drove over to the guy who worked on my tranny to put it up on a lift. Come to find out, I just slightly over filled the tranny and it was coming out the top of the dipstick.
Anyway, to my question....the mechanic noticed that I didn't have a kickdown switch hooked up. The switch is there, but no wires. He told me that I need to install one because the transmission won't downshift if I ever get on it and won't build pressure in the lines...and long term will blow the transmission. Question is, I have no idea how to wire this up. He said it attatches to the throttle somehow, but he was pretty vague in the details. I just nodded my head, smiled and shrugged my shoulders. Is this really necessary and if so, could someone give me some guidance in how I need to rig this thing up? thanks again everyone for all the past help.

Originally Posted by kahouna23

I just installed my tranny after getting a mild shift kit put in by the local shop. After install, I was driving it around and noticed some white smoke trailing me. I pulled over to find tranny fluid dripping on the headers from the TOP of the engine...... I drove over to the guy who worked on my tranny to put it up on a lift. Come to find out, I just slightly over filled the tranny and it was coming out the top of the dipstick.
Anyway, to my question....the mechanic noticed that I didn't have a kickdown switch hooked up. The switch is there, but no wires. He told me that I need to install one because the transmission won't downshift if I ever get on it and won't build pressure in the lines...and long term will blow the transmission. Question is, I have no idea how to wire this up. He said it attatches to the throttle somehow, but he was pretty vague in the details. I just nodded my head, smiled and shrugged my shoulders. Is this really necessary and if so, could someone give me some guidance in how I need to rig this thing up? thanks again everyone for all the past help.

you need the kick down sw, if you cant buy one thats made for the car, i have use like a push botton starter sw. make a bracket on the starter sw. behind the throttle linkage so when you're at WOT the accl. lever will hit the button on the sw. i'll try to get you a pic. you got a pic. denny?

http://store.summitracing.com/egnsea...4&autoview=sku

this is what you need.

Once again guys, thanks for the info. You guys are a great help, man am I glad I found this site!!!

You do not 'need' a kickdown switch. I have been running my TH400 for 7 years without one, and it downshifts fine when I want I get on it. You will not hurt anything without one. This is from a trans rebuilder.

Originally Posted by 1JohnnyO

You do not 'need' a kickdown switch. I have been running my TH400 for 7 years without one, and it downshifts fine when I want I get on it. You will not hurt anything without one. This is from a trans rebuilder.

for your trans. to do what it was made for, you do need the passing gear sw. hooked up. do you have to have it no, you can shift it by hand. after about 35 mph it will not downshift. below that the gov. and mod. reg. the down shift, above that the switch does. this is from a trans. re-builder. did nothing but 350 and 400 trans at a caddie dealer for 3 yrs. "fixed a lot of no kick down shifts."

i do not run a kickdown on my tranny as i dont realy need it for the street the car shifts into 3rd at about 3200 rpm when you get on it, i hooked up a direct switch to the tranny as when i am racing i flick the switch before i stage and run right off the line with the kickdown activated it works fine for me.

Originally Posted by canadianal

i do not run a kickdown on my tranny as i dont realy need it for the street the car shifts into 3rd at about 3200 rpm when you get on it, i hooked up a direct switch to the tranny as when i am racing i flick the switch before i stage and run right off the line with the kickdown activated it works fine for me.

what kind of trans. do you have?

This is interesting. Mine has no switch at all, but it will definitely down shift when Im doing, say, 50 mph, and I hammer it. I have a friend in Ct. with the same engine and tranny in his Chevelle, and we were discussing this about 6 months ago....his does the same thing, and he has no switch either...never had one. So how is this happening?

Originally Posted by 1JohnnyO

This is interesting. Mine has no switch at all, but it will definitely down shift when Im doing, say, 50 mph, and I hammer it. I have a friend in Ct. with the same engine and tranny in his Chevelle, and we were discussing this about 6 months ago....his does the same thing, and he has no switch either...never had one. So how is this happening?

i'd say you dont have a th400

I think I know what I have....and my friend's car also. They are TH400's without a doubt.

Originally Posted by 1JohnnyO

I think I know what I have....and my friend's car also. They are TH400's without a doubt.

a th400 trans. will not down shift after 40 mph, with out the passing gear sw. hooked up. with it hooked up it will down shift up to round 60 to 65 mph. it drops back to second above 40 and it goes to low below 40. if the sw. is not hooked up it want do that. all that you see on the trans is a wire plug. the sw. is on the carb. or hooked to the accelerator under the dash.

this is for anybody that wants to know. the kick down switch on a th400 and the kick down cable on a th350, does the same thing, just in a dif. way. one is elec. and the other is cable. both need to be hooked up and adj. properly for your trans to work like it should. it will burn the clutches up prematurely if you don't. this fits the 70 to 77 chevy. http://cgi.ebay.com/ebaymotors/1-70-...QQcmdZViewItem

hey lt will not activating the kickdown wreck the clutches?
its only activated at approx 3/4 or more throttle opening before causing the transmission to either shift down or stay in 2nd till high rpm?
in my case that is only at about 4200 rpm.
i would assume that if one was operating a really high tourque engine or one with a blower it would generate much more power than i am at 1/2 throttle and kickdown would not be activated at that time.
just a thought

Originally Posted by canadianal

hey lt will not activating the kickdown wreck the clutches?
its only activated at approx 3/4 or more throttle opening before causing the transmission to either shift down or stay in 2nd till high rpm?
in my case that is only at about 4200 rpm.
i would assume that if one was operating a really high tourque engine or one with a blower it would generate much more power than i am at 1/2 throttle and kickdown would not be activated at that time.
just a thought

the kick down sw. dont work on a th400 unless you have it at WOT. if it down shifts at part throttle then thats the modul. or gov. doing that, and it would have to below 40 mph.