[daveymc29]

The easiest part to do is wiring the Lay-cock so it won't get the solenoid energized when the transmission is in reverse, which will destroy of badly damage the O/D unit. Looking at a transmission from the rear yoy will observe there are two cylinders running the length of the tower, one on each side, right and left. Viewed this way with the shift lever up, the tube on the right contains part of the shift mechanism that will move the transmission into 1st and reverse gears. The end toward the rear is where I drilled a hole, threaded it, and mounted a switch to break or make contact as the shifting fork is moved in and out of position. The hole drilled was threaded to take a switch that will be interupted when pushed by the shifter being move to the reverse position. I connected the hot wire feeding the overdrive to a fuse, then to this switch, then tested my work to make sure it broke the current any time the gear shift was moved to the reverse position. One could put another switch on the opposite end of the tube to accomplish the same result in first gear, I felt that unnecessary as I am smart enough to not engage the O/D with to power the O/D when the shifter is in first and no real damage would result if it were engaged. From there you can run the wire from that swith to the on/off switch for the O/D when you want to manually make a shift. Mounted my switch where it was covenient to reach with my left hand, you might wish to make it the opposite as you will be shifting the tranny with your left hand.