thm 400 kick down ?

Ok the detent solenoid gets a 12 volt signal and does its thing. How it gets it is up for artistic interpreting it just needs 12 volts.

???What exactly does it do???

The info I'm finding is quite confusing.
Some say it works without being hooked up, some say it won't.
Some say it changes line pressure at WOT along with forced kick down, Some say it don't.
Because of the line pressure, some want it on a manually controlled toggle
These guys discuss quite feverishly to defend their positions.

Thanks

 

I have a small homebrewed Turbo 400 kickdown switch.



Works GREAT ... especially in the light roadster !!

 

The transmission will kick down if the electric kickdown wire is not installed....but it won't kick down at as high of speed, since it's just using the vacuum modulator signal. Let's see what Chevy has to say about it. Notice the "boost" end of the pressure regulator valve, which is getting "yellow" oil because of the detent.

 

ive run my kickdown on my bucket on a manual switch on the shifter since i built the car. I have a 500 caddy in my car and never would get to the kickdown when accelerating unless i really was getting serious or when i am running at the track. seems to work fine for me but i could see it being harder on the trans in a heavier car to run without a kickdown.

 

Thanks squirrel.

 

I have installed for customers a Nitrous switch from Edelbrock to operate 400 Chevy kickdowns. Works perfect. The difference with or without it is night and day. Since I am a Mopar guy despite working on all makes for others I would suggest you dont hook it up and listen instead to the experts who have never hooked up nothin. That way if I or my Mopar or Ford friends meet you at part throttle on the street we can fry your butt with ease thus saving us fuel and time.
Don

 

I have been manually shifting ( up and down ) my th400, I do not have the electronic kick down hooked up. My trans has a mind of its own, I can hold first, shift to Second at say 4000rpms and it may shift then or maybe at 4500 and it verys, it will only shift when i tell it to at lower rpms, any thought why this might be? I have shifted at 4800 manually and it not shift till 5000rpms. (its a stock th400 no kit, no valve body )

I was wondering if the kickdown may effect WOT upshifts or when you manually shift it like I have been doing.

Godspeed
MrC.

 

Usually a stock th400 will shift at around 4500 if the kickdown is working. Some of them (corvettes come to mind) shift higher, like 5500.

I would expect it to shift earlier if the kickdown is not connected.

Yeah Don, it's really nice having the transmission work like it is supposed to. It's also fun going sideways when you mash the pedal at about 30 mph

 

If my memory is correct, a 400 will downshift into second at wide open throttle, but it wont go into first without the kickdown switch. Its nice when you floor it at lower speeds and want first gear.

 

mine would not step down to first without a switch. First time I jumped on it was a eye opener.

 

That detent looks like it sends the fluid on a much different path.
That's got to have quite a impact on the trans performance under heavy throttle.
Kickdown or WOT from a stop id assume.

What could be gained by having it on a toggle so that it can be signaled at will or part throttle? Or is it just foolishly surmised?

 

The kick down was disconnected on mine when I first got the car. We hooked it up and it is night and day. Much smoother.

I'm curious about the benefits of a toggle switch as well.

 

I can understand why someone would do that, sort of. It will affect the line pressure, because the "detent oil" pushes on the end of the main pressure regulator valve, boosting it up a little bit. So it will have more force engaging the clutches, and be less likely for the clutches to slip at full throttle shifts.

Although it seems to me it would make more sense to just put the switch on the throttle linkage and not have to have one more thing to operate manually while you're going fast. But I guess some folks like the challenge?

 

I'm using a 70's gm gas pedal assembly for the very reason is the switch is mounted to it. Anyone have a wiring diagrahm, squirrel?

 

Yeah. One wire on the kickdown switch comes from the fuse box on a switched fuse, the other wire from the kickdown switch goes to the transmission. It's not very complicated.

 

I knew it was a dumb question, but I thought my trans had 2 spades IIRC ?

 

You have your hands full keeping the car going straight and not ending up in a ditch when it kicks down

 

One spade is for the kick down the other is the infamouse "split pitch"


Godspeed
MrC.

 

If you have money to burn and don't mind a little billet.
http://www.jegs.com/i/Lokar/625/KD-2400HT/10002/-1?parentProductId=

 

I'm still trying to figure some if this stuff out, but it depends on the year, make and weather or not someone modified it.

If its factory Buick olds or caddy 400 unit from 65, 66, or 67 with 2 prongs its a "switch pitch" as Kenny bell called them or variable pitch as the factory called them.

If its a later GM 400 trans with 2 prongs it mosst likely is a TCS system AKA transmission controlled spark.

There is a "however" that applies to the above. Since the switch pitch equipment will bolt into any 400 trans and plenty of modifications have been made thru the years. Your once original SP could have had it removed and your once standard 400 could have had the SP added. you really have no way to tell unless you look at the input shaft.

 

Or just pull the pan and see where the wire inside goes. If it's switch pitch, it will go to a solenoid can on the back of the front pump. If it's a TCS switch, it will go to a pressure switch screwed into the valve body.

 

I used the lokar 400 kickdown assy on my hemi w/400 it made quite a difference on how the trans performed when the kickdown was set up correctly. The nice thing about the adjustment is you can set it up for your driving method and the car it is in. When I dial mine in finally it was like the kick in the ass you want when you floor it.

 

Why would someone jumper the gas pedal switch so that it would be hot 100% of the time ?

 

I don't know...maybe you should ask the guy who did it? A lot of people don't understand how cars work

 

I checked the obvious stuff like an inoperative switch, compromised wires, and the like.
All that stuff checked out.
I actually tried to get a hold of tge guy but number is dead.

I have a couple concerns, did running it full time mess anything up.
Was it messed up and running it full time hot make it work better ?
Them the question of what would having it full time hot do for it from a performance stand point.

It lot drove fine but couldnt take it around the block.

 

It shouldn't shift until about 4500 rpm....unless the circuit isn't getting power, or the solenoid is not working, or something.