I just bought a MityVac hand-held Vacuum Pump and went out to my car, an 89 Cutlass Supreme, to test it out.
One thing I tested, the transmissions Vacuum Modulator, has me questioning whether or not it's faulty, or leaking etc.
I've had hard upshifts as well as shifts into Reverse for a while, and haven't figured out the culprit yet.
Anyways, I pumped the Modulator with 16" hg to see if it held, and it pretty much started to fall right away. It fell to 0" hg in about 20 seconds.
I applied the vacuum at the manifold end of the long metal vacuum line that connects to the modulator. Before I go out of my way to remove the airbox and reach down to the Modulator itself and apply vacuum, in order to determine whether it's the line itself that's leaking, or the Modulator diaphragm, I figured I would first make sure that 20 seconds is too quick for the vacuum to leak-off.
So, does anyone happen to know?? I've done some searches online and find answers anywhere from 1 minute to 5 minutes. I'm not sure if it depends on the Modulator, or if it's a pretty universal figure.
THANKS!:)