Hello guys !! I rebuilt a fordomatic 2-speed for a friend and the tranny shift 1 to 2 very very high (55Mph). The transmission had the same problem before the rebuilding. My Friend use Dexron II transmission Fluid. Any idea to solve the problem ? Thanks !
I had the same problem with a fmx box and it was just the vacuum assist unit that had failed.Cheap to fix.I don't know if your box has one of these but if it has check it out.
The Fordomatic has a manual linkage that controls both upshift & downshift. I dont think there was a vacuum modulator until the early C4. Try taking a little pressure out of that linkage from the carb to the tranny. When it's too tight, the tranny is getting a signal that the accelerator is depressed more than it is, extending the shift point. When it's too loose the tranny will shift too soon, and possibly slip. Somewhere in the middle will behave behave like you want. Sent VIA top secret BIGREDTODD Mobile HQ
thank you for your reply guys The tranny's got a vacuum modulator, I replaced it I gonna check the throttle linkage if you have other idea ...
Some of the later model modulators had an adjustable screw inside the fitting where the vacuum hose plugged in to it. You could adjust in in or out to adjust the shift point. People installed them thinking they could just make a little adjustment to fix their car when by that point they had more problems than that. Plus a lot of times the screw ended up on the floor. Ford did make different length rods that fit into the modulator to adjust the shift point. Did the same job as the adjustable modulator. Shorter pin, shorter shift I think is how it went. Then there the guys that lose the pin and it won't shift at all.
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