TH-400 help

[AL8001 at aol.com]

In a message dated 99-02-24 23:45:41 EST, fraser at forbin.com writes:

>Very good.  I imagined this was the case due to the name "kickdown switch".
>It's a wierd concept, though... why didn't they totally base the shift
>(incl. downshifts) schedule on MAP(modulator) and speed(weights and
>springs)?  I mean, what's really gained by making TPS an input. 

There is a certin amount of hysteresis and delay built into a trans shift
program to pervent up/ down/ up/ down shifting when a slight road speed or
throttle position change occurs. The kickdown tells the trans to down shift
right NOW.  At lower speeds the trans would probably ( with some delay) down
shift on it's own.

<<I guess my question should have been phrased a little more specifically.
Will the modulator and/or vacuum-intended internals burst if it sees boost,
or will successfully firmer shifts be the result of the additional applied
pressure?>>

I'd think the vac mod would be good for atleast 10 psi, probably more.   Look
at for a GM turbo diesel that uses a 400 and follow the vac hook up.   

As for the firmer shifts, hook up a pressure guage to the throttle pressure
tap ( I, think a 400 has one) and the line pressure tap.  Use compressed air
and a regulator attached to the vac mod.  Vary the air pressure and watch the
guages.  If the throttle and line PSI rises with higher air pressure, firmer
shifts may result.

Harold