700-R4 wiring

After rewiring my friends 68 camaro I am left with a purple wire coming off the 700-r4 tranny which I believe is for torque convertor lockup.  The wire runs to some sort of vaccuum switch off the manifold but the other end of the wire is cut.  Ive read it runs to the brake switch but the would provide 12v on braking which doesnt make sense.  Is this wire supposed to be 12v and the vaccuum switch will close when needed? Any ideas???  

there are a bunch of different ways to wire it up...

the important thing is to understand how the lock up system works..

inside the transmission pan there are one or two pressure switches and the torque converter solenoid.

the 2 pole pressure switch closes when the pressure comes up to connect the 2 terminals...

the single pole pressure switch closes and connects the terminal to ground...

these switches are usually on the 3rd and 4 gear pressure circuits...

the vacuum switch needs to be hooked to ported vacuum... so there will only be vacuum when the throttle is opened.. not at idle..

the brake light switch for the torque converter clutch has 4 terminals...    2 for the brake lights.. 2 for the torque converter clutch ...    

this is how the brake light switch works...   normally the button on the end of the switch is depressed by the brake pedal when your foot is not on the brake pedal...   in this position.. the brake light contacts are open... the TCC contacts are closed...    when you step on the brakes... the stop light contacts close..  and the TCC contacts open...  this stops the power feeding the TCC circuit... so the torque converter clutch will release...



the vacuum switch should be hooked to ported vacuum...  NOT MANIFOLD vacuum...  ported vacuum rises with increase of engine speed... none at idle.. you will have to test the various ports on your carb...  not all carbs have a ported vacuum port...  so there may be a problem there...

you can just have a toggle switch that runs to the 4 pole brake light switch and then to the trans...  and depend on the various pressure switches make the circuit. they do work...

what did i forget...

there is a lot of information out there... on this subject... if i notice that i have missed something...  i will edit.. i sure there are other opinions...


the brake light switch  autozone # DR497 will work as it has the 4 terminals, 2 for the brake lights, 2 for the cruise control..