[mr0077]

Curt, your description was right, except where you hook up the transmission. Refer to the photo, and you'll see that the same 12V going to the contact terminal should also go to the trigger terminal (more on that in a second). The other side of the trigger terminal goes to the transmission. If it is a one-wire trans switch it grounds internally...if it is a 2-wire trans switch, the second wire should be grounded to the frame, trans case, etc. With this wiring layout, you use the starter wire to energize the relay.
An alternate way to wire the relay is to have a 12V (FUSED!) wire going to the 12V "in" terminal and the ignition starter wire going straight to a trigger terminal, so all the starter voltage would do is trigger the relay, and the 12V in would energize the starter. The 12V out still would go to the starter solenoid terminal and the other trigger terminal would still go to the transmission...did that make any sense at all?
And also, I am assuming that what they call 12V in and out are shown as passing through the contacts on their diagram (theirs should be similar to mine in the photo). Good luck!