Under the battery tray. The battery and battery tray needs to be removed to gain easy access.
look under the battery tray
It is under the battery rack. Remove the battery and there are three bolts in the engine bay and one in the fender well.
Test it with a vacuum gauge.
Under the battery Plate.
under the battery, remove the battery and battery tray
check for a vacuum leak.
spagettie
check your local library for a manual with diagrams..free or penny up and buy a manual dave
over time the vacuum lines can get clogged with gunk and not allow the actuators to engage the trans axle, so replace all the vacuum lines and if it still doesn't work its probably a bad actuator or the motor on top of the transmission.
I have a 1988 chevy s10 pickup 2.8. I went to the service department at my local chevy dealership and they printed out 3 diagrams for me for free.
Check under the battery tray.
You need a vacuum pump designed for that purpose.