Originally Posted by revspan
oops, I looked closer at your post(ovrdrv), and now see that the relay in your drawing is not part of the transmission TC lockout. Sorry, I should have looked closer.
The inline photo of my wiring for the TCC does indeed use a relay as does the WiKi linked diagram.
One could do it without a relay but I've found a relay helps unload the switches and lets you use smaller wiring in your control section. Each to his own, I prefer to use relay for nearly everything these days.