The wire is at the pcm on the firewall. It is also year specific. Google year and trans converter lockup switch. U will get the pin # at the pcm run that to one side of a toggle switch and the other side of the switch to ground, voila lockup in 2,3,and 4.

 

https://www.dieselbombers.com/5-9l-1...ic-repost.html

 

I am in the same situation. I tried using toggles for od and tc lockup, neither worked, im going to clean out my 8 pin plugs with cleaner on both ends to make sure i have a solid connection, then meter out the supply wire to the plug to make sure i have power, if i do then the solenoid is bad. Another thing you can check before draining the pan is on the drivers side of tranny an 11mm plug about 4 inches above vb. take the plug out and blow compressed air in there. If it sounds like air blowing in the tranny the od piston is bad and may need a rebuild. If it sounds like the piston engages crisp and tight your ok. I havent tried that yet either but i am in the same position as you and a guy told me to try these and get back with him. I hope this helps you out.