TH-400 kickdown switch ??

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07-21-2006, 03:53 PM
kahouna23

TH-400 kickdown switch ??

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.
07-21-2006, 04:25 PM
lt1s10

Quote:

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?
07-21-2006, 04:32 PM
lt1s10

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

this is what you need.
07-22-2006, 06:37 PM
kahouna23

Once again guys, thanks for the info. You guys are a great help, man am I glad I found this site!!!
07-23-2006, 02:15 PM
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.
07-23-2006, 03:54 PM
lt1s10

Quote:

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."
07-23-2006, 07:21 PM
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.
07-23-2006, 07:25 PM
lt1s10

Quote:

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?
07-23-2006, 07:27 PM
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?
07-23-2006, 07:28 PM
lt1s10

Quote:

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
07-23-2006, 07:30 PM
1JohnnyO

I think I know what I have....and my friend's car also. They are TH400's without a doubt.
07-23-2006, 07:42 PM
lt1s10

Quote:

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.
07-23-2006, 08:25 PM
lt1s10

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
07-23-2006, 09:16 PM
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
07-23-2006, 09:25 PM
lt1s10

Quote:

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.
07-23-2006, 09:29 PM
canadianal

off the kickdown subject a hair i just put a shift kit in my 400 tranny a bm shift improver,seems to work pretty good.
the instructions said to remove the yellow accumulator spring.
what does this do as i could not quite understand the logic behind it,more pressure maybe?
07-24-2006, 12:18 AM
kahouna23

The B&M kit I had installed seems to be working well for me too. I have noticed that with no switch the tranny does downshift below 40 like everyone says, but above that I need to slam it into second manually. I really love my ratchet shift!! I'm kinda torn between whether or not I really need this thing hooked up. Some seem to think it doesn't do any harm, and some say it does. I mean honestly, in a moderate street rod what do you suppose the life expectancy of a tranny really is? 2, 4, 6, 8 years? Guess it all depends on how much you "simulate the 1/4 mile between lights"
07-24-2006, 04:32 AM
1JohnnyO

It's a mystery to me then. Im not gonna worry about it. As far as the early wear question, Im not doubting anything, but my friend's car has over 12K on it now with the 'no kickdown' thing, including many passed down the 1/4mi....no problems to date.
07-24-2006, 06:24 AM
lt1s10

Quote:

Originally Posted by 1JohnnyO

It's a mystery to me then. Im not gonna worry about it. As far as the early wear question, Im not doubting anything, but my friend's car has over 12K on it now with the 'no kickdown' thing, including many passed down the 1/4mi....no problems to date.

if he is shifting by hand you dont need the sw.
07-24-2006, 06:32 AM
lt1s10

Quote:

Originally Posted by canadianal

off the kickdown subject a hair i just put a shift kit in my 400 tranny a bm shift improver,seems to work pretty good.
the instructions said to remove the yellow accumulator spring.
what does this do as i could not quite understand the logic behind it,more pressure maybe?

the accuml. spring don't make the accuml. piston close quicker, its used as a cushion. take the spring out makes the band, accuml. piston slam closed. dont have nothing to do with the pressure.