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I have a 76 ford f100 with the 300 inline 6 thats having trouble down shifting and upshifting repeatedly friend of mine said it was the transmission speed sensor but I can't seem to find that anywhere any ideas
There shouldn't be any electronic speed sensor, unless a newer drivetrain has been installed.
I think non-electronic automatic transmissions use a piece which spins, and has flyweights which expand under centrifugal force, and I think that acts as a speed sensor. But I forget what the dang thing is called! Servo?
Either there's a problem, or the truck is trying to tell you that it's a "hunting" truck!
X2 on last time you have changed the fluid and filter? Also here is some talk about the modulator.
"Check the vacuum modulator and the line that goes to it. Check the line for kinks or other problems, make sure it hasn't come off.If the line checks out, take the line off where it connects to the modulator. If trans fluid leaks out, its bad. If no fluid, it still could be bad. They're simple to replace, disconnect the vacuum line, remove one bolt that holds the clamp in place and the modulator comes out. It has an o-ring seal.Modulators are identified by the color of the stripe. Pretty much the "go to" one is the black stripe. If they don't show that one in the catalog, go with the green stripe. Avoid the pink stripe. That one is a dual diaphragm version that has two vacuum line going to it. If by chance you have one of these, replace it with one of the other two and use the vacuum line that goes to direct manifold vacuum, cap the other line. When you pull the modulator out, be careful. There is a pin that goes in the modulator. Sometimes it comes out with the modulator, sometimes it stays in the tranny. If it comes out, don't lose it."
If the modulator is bad,it usually won't up shift till higher than normal speed is reached. Maybe just low on fluid but things are usually not that simple.If the easy stuff doesn't work,it's an internal fluid leak or the governor is having problems.
