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in a 1990 e4od with a transfer case mounted VSS, can i change the shift points by changing to a different speedo gear?
basically im trying to trick the trans to shift at like 5500 rpm in drive or more without a aftermarket controller. if i use a way lower speedo gear, so for example i am going 55 and the computer thinks im going 40, will it shift that gear at 55 when it would normally shift at 40 because it acually thinks it is doing 40? or does it also base shift points off of the tach? but i have read nowhere the e4od uses any info from the tach except on the 7.3 idi diesels.
but, if it does run on the tach, can i trick it by putting some kind of resistor on the tach wire going to the trans so it thinks its running like say 1000 rpm less then its actual rpm?
and on a 1990 5.8 efi, what is all the sensors the e4od uses to operate correctly?
all i can think of is the VSS, TPS, AND MLPS. and does anyone know if the ecm uses the tach to control the trans?
if anyone can even understand my ramblings, any help with this would be greatly appreciated.
i am going to try tomarrow and swap out my current speedo gear (speedo matched for 4.56 gears and 35 inch tires) to my stock speedo gear and compare the rpms at which it shifts at full throttle to see if the speedo gear idea will work. i have a feeling it wont.
The E4OD looks at the tach for some of the shifting, usually WOT shifts. The tach signal is a frequency, not a voltage. Using a resistor might just make the PCM not see the signal at all. That will really mess with it.
__________________ Mark Former Ford Automatic Transmission Engineer
“The good thing about science is that it's true whether or not you believe in it.” ― Neil deGrasse Tyson
Pin 5 of the TFI module on the distributor goes to pin 4 on the EEC through a 22k ohm resistor, check that resistor and the wire for continuity and if good replace the TFI module, be sure to get another grey one and not a black one.. it is wired differently.
Mark thanks, I found this... Your speaking of this resistor?
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