Vnomous1 Posted April 30, 2010 Report Share Posted April 30, 2010 Hi guys, I am finishing up a 88 durban automatic (all my other SQ's are manuals), but have a question about the transmission vacuum modulator. Their is a small metal tube that goes from the intake manifold down to the side of the transmission where the vacuum modulator is. When I first saw the tube, the end by the transmission had a screw stuck in it (I guess to stop the vacuum leak). Is this tube supposed to be connected to the vacuum modulator? If so, why? If not, what is it suppose to be connected to? Thanks. Link to comment Share on other sites More sharing options...
Bill Hincher Posted April 30, 2010 Report Share Posted April 30, 2010 the engineers used the vaccuum signal from the engine to determine how hard the trans shifts up, whether under load or high RPMs or low speeds, thats how the trans knows to shift hard under acceleration or soft under light load there is a rubber diaphram in the vaccuum modulater that gets moved by the engine vaccuum to adjust the shift, so it is a direct connection Link to comment Share on other sites More sharing options...
Alan Posted April 30, 2010 Report Share Posted April 30, 2010 Bill is correct in his explantion. Should be hooked up. Sounds like it was disconnected for a reason. Are you losing ATF thru the modulator? If it's shot and leaking ATF when you hook it up the intake will draw fulid in during off throttle/idle situations. The tail pipe will look like a smoke generator. Happened to mine. I installed a new one during rebuild and screwed it up putting it in. It's a 2 part deal stamped together. I used slip joint pliers to tighten it up good and snug and ended up turning the outer case against the inner. Guess I broke the seal and wouldn't hold vacum or pressure. It is available thru the Mits dealer, around $45 and NAPA has 2 listed for about half that. Link to comment Share on other sites More sharing options...
Vnomous1 Posted April 30, 2010 Author Report Share Posted April 30, 2010 Thanks guys! I bought a new vacuum modulator to install and will hook up the vacuum hose. As of right now, I have not driven the car it is up in the air on jack stands....a familiar scene for most of us I am sure, LOL. Thanks again! Link to comment Share on other sites More sharing options...
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