I get the vacuum switch off late 80,s chevy vans. It is right on the outside of the firewall & has a blue & green wire connector which get also. If the trans. has pipe plugs on the side for 3 & 4 gear testing I put a 2 prong oil pressure switch in the 4th gear pressure outlet. Wire it all together with a hot wire when the switch is on. Put a vacuum hose from ported vacuum to the vacuum switch. Works great.It releases under heavy throttle & when you let up.
