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Originally Posted by rblookc
Brian,
yes I have a blue modulator that vacuums the transmission on the Driver Side. That's where the vac is good from the booster line but sporadic to the transmission when revved while parked, cranking on the throttle arm (not driving). What I dont get about it is the VCV does not seem to be attached to it. The blue modulator gets vac from the booster and delivers it to the tranny. The VCV gets vac from the booster from a different place on the line (right next to where the modulator gets vac). I am trying to figure out if the line coming out of the bottom of the VCV is just the vent line, because it currently connects to nothing.
As for VCV adjustment, I have a question: If there are two small nuts behind the cone cap on the VCV, which does what? I cant imagine adjusting the vac regulation without knowing which nut to screw where.
Thanks in advance.
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OK, that big blue valve on the driver's fenderwell is called the vacuum amplifier (VA) It's not the vacuum modulator.
You must make sure that all the connections are hooked up to the VA. There is an input for straight vacuum. There is an input for modulated vacuum from the VCV. There is an input for boost pressure from the manifold. And, finally, there is an output to the transmission.
The valve functions in a rather screwy way. It typically provides about 10 inches of vacuum to the transmission under most driving conditions. Then, when you step into the pedal about 2/3 of the way down to about 3/4 or so, the output drops down toward 5 psi.
Then, finally, when you get into heavy boost, more than 3/4 pedal, the valve will drop the output from 5 down to about 1.5 or so.
You need to connect a proper vacuum gauge to the output of the VA and watch the gauge while you drive the vehicle. See if it performs in a similar manner as described above.
In your previous testing, you may have seen proper modulation from the VCV, but, the VA doesn't seem to reflect this modulation. This "appears" to be quite normal as Dave has the same situation on the W124.