TH-400 help

[Jennifer and Brock Fraser]

Thank you all for the advice.  Some more comments....

>>1.  The trans has a wire labeled "kickdown switch".  What does this do,
and
>>do you ground it or supply +12 to activate it? (I assume +12v, since there
>>are no other wires and grounding could be through the case)
>
>This wire is connected to a solenoid valve.  It drops the trans from third
to
>second gear when the throttle is over ~85%. Possibly to first as well, but
I'm
>not sure.   Just add 12V to operate, the solenoid grounds through the case.


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.  You can
tell I live in a electronics realm....hehe  This trans is "ancient, but
sturdy".


>>2.  Does anyone see any problems with deleting the speedo sensor, since
the
>>speedometer on my car takes its reading from the differential, and I'll be
>>using a manual transmission calibration with the PCM... (96 LT1)  I think
>>the only thing that a manual cal uses the speedo for is idle speed, and I
>>can do without that.  Error codes aren't a concern...
>
>Speedo Sensor?  Are you refering to the speedo cable port/ gear on the side
of
>the trans?  If so, not a problem.  Just use a freeze plug or a block off
plate
>from a 4 wd truck.

Thanks for the block-off options, but what I was really referring to was the
impact of eliminating the VSS input to the PCM when using a manual-shift
calibration...

>
>>3.  There's a modulator on the side of the case.  What does a modulator do
>>when it sees boost pressure?  Should I use a check valve to block boost
from
>>going to it?
>>
>A 400 uses the modulator to generate throttle pressure and vary line
pressure.
>With limits, high line pressure at boost would be good.  Higher throttle
>presure _may_ make the trans shift too late under boost.   Not sure if a
check
>valve would help.

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?


>
>>4.  How do you adjust the wide open throttle shift points?  I realize that
>>the trans must be disassembled.
>
>WOT shift points 1-2 and 2-3 can be moved upwards and downwards by changing
>govenor weights and springs. Just take the four bolt cover off the side of
the
>trans to remove the gov.  You may need to have the trans on a slight down
>grade to prevent fluid loss.    B & M sells the spring and weight kit.
>
>To change the spaceing between the 1-2 and the 2-3 shift, the valve body
must
>be removed and the 1-2 or the 2-3 shift valve springs changed.  For the
shift
>kits I've seen, none alter the spaceing between the 1-2 and the 2-3 shift.
>All concentrate on quick shifts and highter line pressure.

Great info.  Thanks.
-Brock