Yo Bronconnoisseur,
Pull the vacuum line off the mod. If fluid comes out of the vacuum line your modulator is no good.
Check vacuum line to modulator from engine intake manifold source.
See Vacuum Gauge Diagnosis - BEST!; Normal engine; Steady gauge 18"-20" at all speeds..." READ MUCH MORE
Source: by Craig U @
Reading your vacuum gauge
Vacuum Modulator; The vacuum modulator is a vital component of an automatic transmission. It tells the transmission what kind of load is being put on it allowing the transmission to react with the proper line pressures and shift points. Over time, modulators can develop leaks, get ruptured diaphragms, get bent, etc. Not only can this cause annoying drivability issues, it can lead to premature transmission failure.
Inspect vacuum modulator, and it's vacuum hose back to intake manifold for leaks, etc.
It's at rear of C6, passenger side..
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