post from another site-- Ill give this a try
"I have a TH400 in my 69 C-10. Recently I learned the transmission requires the kickdown detent circuit be hooked up, which it isn't.
Also I just read that not having it hooked up will accelerate wear on the clutches (FYI to anyone out there with a TH400), and may cause it to up-shift prematurely (which mine does) so I'll be hooking mine up ASAP.
It'll require the install of a kickdown switch (stock item on older cars, but mine never had one) which I'm getting Monday ($45 B&M Kit includes switch, spring, attachment parts, etc for mounting near the carb).
What I also learned is that my particular trans has two spade terminals sticking out where most TH400's only have one. They are arranged in the shape of a "T".
Apparently, the vertical part of the "T" is where the pos 12 volt connects (that comes in from the key-on side of the dash, then via the kickdown switch) to the kickdown detent solenoid inside the trans.
The second terminal (Horizontal bar/top of the "T") apparently grounds the TCS switch (which isn't there any more) when the trans is in 3rd gear.
Confusing things some, the double connector on some 65-67 B.O.P.C.s could be an indicator of a "switch pitch" stall speed torque converter option. Am pretty sure I don't have this because I think I have a Chevy TH400 transmission.