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Discussion Starter · #1 ·
O.K., the saga continues. In the conversion of my 72, now I'm working on the engine harness. Question is, since the old 350/350 is gone, and I've replaced it with a 454/turbo 400. Beings that this is my first auto trans., I'm not real sure as to what I need for electric control of it.

1. What wiring do I need for the transmission? I notice on the diagram there is a tcs control, beings that I have converted to a holley w/out the tcs controls, what does my turbo 400 need to operate properly? As far as I can tell, there is only one wire that run's to the transmission, a black wire that is in the same bundle as the starter wire's.

2. Can I simply snip off the tcs (two green wires) that ran with the temp sending unit?

If this seem's unclear, there is a reason for that. :rolleyes: If more info is needed I would be glad to provide it, Just let me know what you need to know. Thanks, Dave.
 

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Discussion Starter · #3 ·
Joun, thank's for the reply. So are you saying that I could go ahead and remove the wire's for the tcs to the carb, and also the black wire that ran down to the trans? I just want to get the harness simplified before I recover it. Thank's, Dave.
 

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Yeah, you can nix the TCS wires. The other wire is probably the transmission kickdown signal. I'm not sure what color it should be on a 71. You should have 12v going to the kickdown switch mounted near the accelerator pedal and then the output of that switch would go to the vertical terminal on the TH400. If you don't have a switch in place, you will need to get one (I think they are about $12 from year one). The mount for the switch should be on all cars I think.

Good luck,

Troy.
 

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The black wire is the TCS circuit ground. A switch in the trans closes when in high gear to complete the circuit. It can be eliminated.

The TH350 trans doesn't have an electric kick down, The TH400 will need it. The kick down circuit gets power from the IGN terminal on the fuse block. power is routed to a switch that makes (closes) on full throttle, a wire from the switch passes through the firewall and routed to the kick down solenoid terminal on the trans. Depending on what the trans was originally installed in it may have two electrical connection terminals. If two- the top, horizontal, is for the TCS circuit, the bottom ,vertical, is for the kick down solenoid.

This is a pic of the kick down switch and the mounting bracket. It was used on many 68 - 72 GM A-body cars.
 
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