Th400 3speed in 88 chyenne

[joep88cheyenne]

Okay another tranny question. My new to me 88 cheyenne 4.3l has auto tranny. Dab is not original so shows 4 speeds (includes of as 4th) but the tranny is an the 400 3 speed . The modulator was not connected and neither is the electronic kick down. My grandson connected the vacuum line to the modulator. I am running several different thought trains on the electric kickdown.
I am in the hospital recovering from loss of toes due to infection ( gas pedal foot) so have time to figure. I'll be out soon I believe so I want to get back and get that issue resolved. Do I need it no but it would be nice to have the kickdown working like it should. Any thoughts on buying or making one (bs degree on electronics).? And where the "charging" indicator pin on the alternator? My battery light is constant and I was thinking on using that to give volts to a switch to the tranny since it is only hot when running. Guess that is enough for now.

 

[RichLo]

Your right... for trans life, you really don't need one with a 4.3 in front of it. But for drivability, you definitely want one with a 4.3 in front of it, lol.

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[RichLo]

Wait, your battery light is on constantly? Like your alternator is dead? The light comes on when the voltage drops below a threshold. You should be around 14.5v when running and 12.6 after its been sitting over night

 

[joep88cheyenne]

Wait, your battery light is on constantly? Like your alternator is dead? The light comes on when the voltage drops below a threshold. You should be around 14.5v when running and 12.6 after its been sitting over night

Has a volt meter right above it.. always above the 12.5v mark.. no it is the charging sense feed from the alt

 

[Schurkey]

The GMT400 vehicles with the TH400 (3L80) used the computer to control kickdown.

Kinda guessing your computer isn't set up for that. The aftermarket kickdown switch is probably your best bet.

I've put TH400s into 64--72 GM A-bodies that didn't originally have them, but I changed the gas pedal assembly for one that used the gas pedal mounted kickdown switch. I don't think that's an option for the GMT400.