As additional information, the car is not computer controlled. Carb is QJet with standard TV cable bracketry and vacuum HEI distributor. Installed in a street rod.

John

 

The factory wiring uses the four-pin plug on the trans. Pins A and D are the two wires from the solenoid coil in the TCC valve. The factory applies 12V through the brake switch to one side of the solenoid and the computer closes the circuit by grounding the other side. The brake switch is normally closed (to provide power when the brakes are not applied) and opens when the brake pedal is pressed. There is a fourth gear pressure switch inside the trans that normally provides a ground signal to the computer in first, second, and third, and opens that circuit when the trans shifts into fourth. The computer uses this signal plus the MAP sensor, distributor RPM signal, and the TPS to figure out when to lock and unlock the converter.

Without seeing the details of your installation, I can only guess, but most people who retrofit a lockup trans without a computer do a couple of things. First, the OEM internal pressure switch is replaced with one that is normally open, so that it is only closed when the trans is in fourth. If a two-wire switch is used, this is usually wired in series with the TCC solenoid such that the solenoid is only powered when the trans is in fourth. This wiring is usually internal and thus won't be visible until you drop the pan.

The brake switch wiring is usually unchanged and provides power when the brakes are not applied. The vac switch replaces the MAP sensor and computer, and is intended to unlock the converter under part throttle acceleration conditions where the throttle isn't pressed hard enough to downshift the trans. This vac switch can be wired into either side of the TCC solenoid. Usually the vac switch wants to be connected to manifold vacuum, not ported vacuum, by the way.

So that's all there is to it. +12V comes into the trans on one wire, via the brake switch. The fourth gear switch is wired in series internally, and the other wire provides the ground for the solenoid. The vac switch can be in either of the two wires - it works the same either way.

 

The trans was rebuilt before being installed in the street rod and probably modified to run without a computer.

Is the 2 prong plug on the passenger side unusual? I thought maybe it was an external connection to the 4th gear pressure switch which then routed power over to a self grounded solenoid via the wire to the drivers side -- but I'm just guessing.

John

 

The "jumper" wire from the passenger side 2 prong plug to the drivers side 4 socket is shown in my photo gallary in the "2004R Transmission" photo.

John

 

The "jumper" wire from the passenger side 2 prong plug to the drivers side 4 socket is shown in my photo gallary in the "2004R Transmission" photo.

John

That is a pressure switch. Apparently rather than change the internal switch, whoever did the original installation simply put a pressure switch in the fourth gear test port. That's pretty clever. Normally that port on the passenger side has a plug in it and is used to install a pressure gauge for diagnostics. That switch takes the place of the internal one and just makes contact when the trans is in fourth gear. Looks like it's simply wired in series with the TCC solenoid.