factory wires that control lockup go into the driver's side of the transmission case. The factory plug has two or three wires going into it. The BTO kit only has one. There are also some wires going to the brake switch mounted under the dash and is controlled by the brake pedal. It causes the lockup to disengage when the pedal is pressed. Depending on your year 700r4, or if you have a computer in the blazer, you will have other wires coming from the passenger side of the transmission going to the computer (IIRC) and maybe something coming from the brake switch. I can't remember.
The BTO kit has a new piece that goes into the trans, from the pan, I believe this is was controls the pressure to the lockup, it is powered from the wire going into the driver's side.
It's been a while since I installed this stuff. I don't remember the details, but it works well. As soon as the trans shifts into 4th, it is locked. If if step on the brake pedal, it's unlocked and depending on speed, either stays in 4th unlocked for a few seconds, or drops to 3rd.
