I have read numorous articles all over the place and need some clarification. Some say the 400 uses a full vacuum port for its kick down and some are saying it needs a switch installed. Are certain years different than others? I see many other mentioning wiring up the switch to the gas pedal and other different ways. What am I missing?
They all electrical all the th400's ive seen anyway, a micro switch on tbe carb is the easiest way if you dont have the factory pedal and bracket the hookup is just 12volt in 12 out ,if the trans has the two prong plug I think its the top horizontal blade for downshift but not certain but most trans will have just one prong, 2 prong was for switch pitch and California emission cars, so ive read somewhere
Definitely different years are different, but I think all are electric and use some type of switch. They only use vacuum for the modulator, which is different than the kickdown switch. What year/model/engine/trans?
my lark is a frankenstein car with a 455 paired with the 400. I see the vacuum line ran up to the intake and looked underneath and see the plug mentioned. It does have two prongs, one verticle and one horizonal. It was covered in gunk so I never noticed it. Looks like I am going to have to order a switch kit. From what I can tell reading it looks like the 400 is both vacuum controlled and electonically or is that vacuum line for something else?
The vacuum hose runs to what's called a modulator. It uses intake manifold vacuum to get an idea of where you have the throttle open (more throttle = less vacuum) so the automatic UPshift points will be higher as you have the throttle open more. Detent (kickdown, downshift, passing gear) is electrically controlled. Open the throttle to the switch point, the trans may downshift automatically and give you "passing gear". Don't confuse the two functions. Devon
The kick down works off the electric switch. I have a few if you need one. its easy I just hooked a wire from the ing on my fuse box to the switch and another from the switch to the trans. when the gas pedal is at wot it closes the circuit and sends 12 volts to the trans that activates the kick down. ---------- Post added at 08:41 PM ---------- Previous post was at 08:41 PM ---------- The vacuum mod is just to help the trans shift gears
CARHEX: Where do you have your switch at? I see some run it at the gas pedal and others at the carb. I am running a Holley 850dp so curious where others run theirs. Def would be interested in one of the switches and how yours is hooked up if possible. Thanks
Theyre are brackets made that will bolt a common micro switch to the body of the holley, it would be just as easy to use the factory bracket and pedal I suppose just another way to skin a cat
I ran mine to the gas pedal. they do make an after market one that goes to the carb. I can email you pictures just email me at carhex73@yahoo.com and I will reply with the pictures
The kickdown prong is the bottom, vertical on all TH400s. If there is a horizontal top prong, it is for the switch pitch function on 60s transmissions, or emissions controls on 70s transmissions. Bruce Roe
Is there a way to decode the number on the trans to tell what year it is? I didn't drop this motor or trans in so I am assuming it is a 70's th400 as its a 70's 455 however it would be nice to be certain. I heard to test you can apply 12v to each prong and if the bottom prong (verticle) clicks then the kick down solenoid is good and if the top one (horizontal) clicks that will determine if you have the SP trans. If its not a SP would the 12v test mess up the emissions advance or whatever the top prong would be?
There should be a plate (1x3" or so) riveted to the trans on the passenger side. It will have the serial number of the car it came from and 2 big letters on it, like OS, BB, BA, OW or something. If you post the letters someone will probably know.
Wicked, On the passenger side of the transmission is a tag. (riveted to the case) That tag has the model year and a 2 letter ID code. That will tell you the year of the transmission, and what make, model, and engine it was installed behind. ALL THM400's have an electric kick down, all of them. The vacuum line goes to the vacuum modulator on the passenger side rear of the transmission. Very simple in operation, apply 12 volts to the vertical contact on the driver's side of the transmission, it downshifts. At least as important, is the model year car you are installing it in. The 68 and up cars have a switch that attaches to the gas pedal bracket. That switch is activated by the gas pedal and sends 12 volts to the transmission. The 65-67 cars had a different kind of gas pedal, and the switch was mounted on the throttle linkage. That switch also controlled the switch pitch. The ID code will also tell you whether it is a switch pitch.
I will pull the numbers and letters off the tag, highly doubt its a SP but with this thing anything is possible. I see you mentioned 65-67 the switches were at the throttle linkage and 68+ were at the pedal, how about 64's?
Not sure about the 64's, but my guess is also throttle mounted. Are you going to tell us what year car you have?:grin:
Looks like it's a 70 th400, code is 70 Bc. Car is a 64 with a 70 or so 455, still trying to clean it up and see the engine number.
Just wanted to see if anyone has used the Lokar kick down set up for the 400? I just bought a new set up with everything needed for $40 so looks like this is the route I will be going. The kit has a remote mount box instead of having to hook a switch up at the carb or pedal. Anyone have any experience with these?
I'm not sure what you have. But beware of putting an electric switch down under with the trans. Moisture can oxidize over the contacts before long. Bruce Roe
its not your conventional type kickdown switch, below is the set-up. http://www.lokar.com/product-pgs/throttlecables-kickdowns/tc-kd-pgs/th400kd.html
