I have recently swapped out my tbi for edelbrock multi-port fuel injection on my 454 1 ton chevy. I removed my factory ecm computer to install edelbrocks computer. Well I have a th400 that wont shift automatically because that little orange wire that comes off of the tranny is just hangin there. I couldnt find a kickdown switch at all on my throttle on the tbi or on the gas pedal in the cab. I know theres a transmission relay on the firewall. According to mitchells wiring diagrams the little orange wire goes to the transmission relay then to the computer I no longer have. Is that correct and if so what can I possble do to get transmission to shift. Any help would be great because Im totally stumped.
th400 transmission not shifting
Oct 07, 2007
13 Replies
What year THM400/3L80 is it?
----------------- TheSnoMan.com
Its a 87 thm400.
Its an 87 thm400 and correction to my post I dont have any forced downshifts.
On Sun, 07 Oct 2007 11:57:58 -0700, yblow wrote in :
I may be mistaken but I believe your kickdown is mechanical.
Do you mean mechanical by a kickdown cable?
There never was a cable on it before and it ran fine I just cant figure out were my orange wire goes from my th400 and if the factory computer has anything to do with my kickdown shifting. I cant find a kickdown switch anywere?
On Sun, 07 Oct 2007 12:49:04 -0700, yblow wrote in :
My bad:
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The later TH400's had the detend controlled by:
The TPS, with an output from the ECM.
You'll need to get an aftermarket kickdown switch, from TCI, B&M or maybe Trans-Go.
Read my earlier post.
There never was a cable on it before and it ran fine I just cant figure out were my orange wire goes from my th400 and if the factory computer has anything to do with my kickdown shifting. I cant find a kickdown switch anywere?
I new it so the ecm took the signal from the tps sensor and than sent a signal threw a relay to the transmission. Hey thanks alot for the info just wanted to make sure brfore I spent 50 bucks on a kickdow switch.
My pleasure:
Just remember, it will not only be a kickdown switch.. It will have some sort of module, and a relay to reduce the voltage to the 5 volt signal.(I think)
Good luck, and let me know if I can be of any help.
RK
THM400 has long had electric kickdown. (I had a 68 that had it that way) In cars they used to put a slide switch on gas pedal arm under dash to would force kick down.The wire in question is likely the kick soleniod down wire.
----------------- TheSnoMan.com
Hey thanks alot for your help Im looking into it today Ive still got the factory relay for the truck.
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