Ok, I'm swapping from a T-5 to a 700R4 in an 84Z. Yes, I know the manual is better. No I can't keep one in it without spending a fortune. The point is, I need to hook up the lockup for the torque converter clutch. Obviously, none of the wiring is there to do so, since the car never came with an auto. I know I can buy a kit from B&M or TCI or Bowtie Overdrives or a million other places. I'm cheap, and I don't believe that it really needs to cost a hundred dollars.

I want the TCC to lock up in fourth, and fourth only. It needs to unlock upon applying the brake. I've heard that you can use a vacuum switch, but I get the impression that lockup would be very dependent upon throttle position and would result in excessive lock cycling. If anyone can actually explain this so that it is intelligible, I will gladly right up the mod for the tech articles section so that we can stop asking here.

Thanks,
Dave

 

Use a pressure switch in the valvebody to lock in 4th, and a stock brake pedal switch to unlock when the brake is applied. If you use a vacuum switch, the setpoint is low enough that it mostly only unlocks at WOT.

 

So, how does the pressure switch work? Where do you get said pressure switch? (I called the local gm dealer and they were just confused) And how do you actually wire all this up?

 

The pressure switch screws into a pressure port in the side of the valvebody that has pressure when the transmission is in 4th gear. You can get it from GM, a search will turn up the part number.