On the 440T4 Automatic Overdrive transaxle the modulator is on the front of the case, A vacuum line leads to it from the intake manifold.
It hooks to a vacuum port on the intake manifold behind the carb.
The vacuum lines on a 2000 Chevy Silverado run between the intake manifold and multiple valves across the top of the engine. The vacuum pressure is generated by the engine's compression.
If you have power brakes look where the large hose that goes to the brake booster connects to the engine and that is your main vacuum source.
In the line that hooks to the passenger side of the intake manifold.
from the intake manifold.
on the drivers side of the fuel rail part of the intake manifold, it has a vacuum line connected to the top of it.
on the intake manifold you should see a vacuum line coming from it connecting to youe throttle body
There are about 20 vacuum lines. Do you mean a main intake manifold line?
The PCV valve is located on the top of the valve cover. There will be a large vacuum line connected to it.
The vacuum line diagram on a 1985 Chevy Pickup can be found in the service manual. It details not only the location of each line, but its function as well.
the line is connected to the carburettor if you have one or to the intake manifold after the throttle valve. The purpose is to connect intake vacuum to the booster.