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I have a 1994 Aerostar AWD XLT given to me from a friend. Problem is that 1x/mth I have to add tranny fluid because it starts to slip. Friend told me the tranny fluid was somehow getting sucked into engine, there are no visible signs of leaks under van. After countless hours of multiple forum research(thanks to all) I see it is either the "transmission modulator valve diaphragm" or the "vacuum throttle control valve diaphragm" that needs replaced. Where are they located? How easy to replace? Can diaphragm only be replaced? What are part numbers? Where do I get parts? Anything else to replace due to this while I'm at it, or will just this be fine? Any online schematics/drawings? ANY help would be most appreciated!!!!!!!!!
Does the 1994 models still use a vacuum modulator? If so, it's located on the passenger side of the transmission, behind a heat shield near the catalytic converter. It uses engine vacuum to control some shifting events through a rubber diaphram. If the diaphram is leaking, it can suck ATF into your engine, as you describe.
Look for the vacuum line going along side the passenger side of the transmission. It will be a thin metal line that eventually connects to ta short section of rubber line that connects to the modulator. Pull the line to see if there is any ATF in it. If so, you need to replace the modulator.
xlt has hit another home run
thru mid model year '95s had A4LD with vac. modulator
$25 part
careful to not lose the steel actuator pin inside at the end of the modulator shaft, sometimes comes out with modulator