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TH-400 "sportmode"

Hello Group,

Any GM TH-400 automatic transmission gurus here? I ran across an idea whilst looking for info on a B&M Transpak kit. I installed the kit and love the change. The new idea was to install a switch in parallel with the TH-400 "kickdown" switch, that would allow you to "turn it on and leave it on". Here's the theory... If you actuated that switch, under light throttle,high vacuum, wouldn't it still shift "normally"? THEN if you drove harder wouldn't it then hold each gear to the customary "kickdown"

5000 rpm before a shift taking place? IF it does indeed work this way, would it hurt anything? You could just switch it on or off. Since the switch is in parallel, turning it off would just put it back to "normal" mode. Is my logic off on this concept, or am I missing something stupid and obvious?, Thanks Adysthemic
Reply to
Adysthemic
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"Adysthemic" wrote in news: snipped-for-privacy@giganews.com:

There is no point in doing this. It will not shift normally if the kickdown is switched on no mater the throttle setting. that is what the kickdown switch does. if the kickdown switch is working ok you do not need any other mod. KB

Reply to
Kevin

Erm,uh, I don't want it to shift "normally" in this mode. I would like it to hold each shift to 5000rpm, then shift. Then I'd like to flip a switch and go back to "normal". I believe that I have analyised the "problem" as thoroughly as I can. Perhaps you do not fully grasp what I am inquiring about. Adysthemic

Reply to
Adysthemic

Perhaps you do not fully grasp what I am inquiring about. _______________________________________________

Tell it like it is, Adysthemic. You're sure to get a lot of advice and help that way.

Rodan.

Reply to
Rodan

Won't work that way. With the kickdown engaged the trans won't shift. The kickdown solenoid only diverts fluid. If you try to engage it in other gears it will act like it's in neutral.

Reply to
Steve W.

Steve,

Do you think just trying out my theory will have any delitrious effect, or will it just not work? I want to "turn on" the kickdown switch, leave it that way, and drive around in a spirited manner. I theorise that each gear will hold to the limit of the mechanical governor,then shift, when throttle position is such that the vacuum modulator sees little signal due to wide throttle opening. I also think that driving very gently would produce no discernable difference in tranny behaviour. What do you think? Would trying this hurt anything? Adysthemic

Reply to
Adysthemic

Good way to burn out the clutches through the slipping when they don't get full pressure because of the diversion from the KD.

What you are attempting can be done but it isn't a simple thing. You would need to alter the governor and the valve body so that you would still have full pressure shifts. The other item is that unless you have an engine that can handle those shift points you will probably snap the crank on about the third shift. The engine is going to be way off the torque peak when the shift occurs which will mean instant lugging and constant hunting as it tries to keep up to speed. It will act a lot like an impact wrench connecting the engine and the trans. Even the converter won't help much unless you replace it with a very high stall to help absorb the shock of the shifts.

In all I wouldn't even try it unless you want to buy a new transmission really soon. And possibly a new engine as well.

Reply to
Steve W.

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