my th350 has the vaccum htingy on it... how do i use it?
10-25-2007, 07:58 PM
#3
The vacuum thing is actually called a vacuum modulator. It requires a constant vacuum signal from the engine as opposed to a ported signal. The vacuum modulator regulates shift points according to engine vacuum to make the transmission upshift at lower rpm during part-throttle driving. From the factory, instead of a long rubber hose it had a steel tube with rubber hose ends on it. That steel tube was used because over time the rubber hose can collapse and interfere with the signal!
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10-25-2007, 09:40 PM
#4
I would run a steel line to reduce the risk of the line melting or rubbing through. Use 1/4" brake line. Works well and can be bent easily by hand if you do not have a tool for bending it. Install it before putting the trans in so you can follow the contour of the trans. I use to follow the dipstick up and go from there in the old days. I guess depending on where you are going to tap into, will determine as to where to run it up. Another tip while we are on the subject. The modulator is adjustable. If you look inside the modulator where the line connects there is a small set screw. This will help to adjust the shifts to a degree. If it shifts early turn the crew clockwise or in. If it shifts later then turn it counterclockwise or out. If these adjustments do not get you to where you want to be then it will be time for some governor adjustments. This is accomplished with a governor recalibration kit. With this kit you will be changing the springs and or the weight of it. This can be very difficult and takes time so do not be discouraged if it takes more than one shot at it. Make sure to document what changes you make while doing it. This will help you return back to a previous setup if you go the wrong direction. Good luck. Vince
