FMX kickdown
#1
My FMX kickdown works  but if I floor it in D it only holds onto 2nd until 4,500 before it changes up, I've screwed the module ( blue one) screw in a half a turn to see if it changed but it didn't, is 4,500 too low, I was expecting 5,500 or so.

From what I've read it could be the trans governor but to be honest I dont want to take the back off to see if it's sticky.
What does moving the screw in the modulator do?

I've had the two rubber vacuum modulator pipes off to check they are not leaking or collapsed but they seem fine.
on the opposite side of the box to the modulator is a steel pipe pointing down with a witness mark where I guess a rubber pipe was once, is it just a drain pipe or should It connect up to something  Huh

I know FMX boxes are not popular but if they are as bulletproof as people say that is worth far more to me over here as access to C4 or C6 boxes is not easy here so I will keep it until I or it dies.

Thanks for any help  Thumbup
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#2
Ok I'll try to get this old brain to remember all the finer points of the FMX tranny. As this box was designed in the late 50's and had several improvements over it's life. I believe if you leave the shifter in drive it will shift exactly as you describe. Now the interesting thing is if you pull the shifter into low gear, it should stay in low gear, and not shift out. It should allow engine braking, as it's still locked in first gear. If you accelerate, and shift to 2nd. It should stay locked in second gear, and also allow engine braking, if you back off the gas. It should stay in whatever gear you put it into. Once in drive it will function as a regular automatic. The kick down is simply to shift it down to 2nd / passing gear. It does not hold the trans in second. It sounds like the modulator is either the wrong one, as it should go higher then 4500?  Either that, or your not making enough engine vacumn (Radical Cam) and it's causing it to shift early. I treated my FMX like it was a stick, and shifted it manually if I wanted to go fast. Otherwise I  just left it in D. 

Try to find the oldest transmission shop you can, and find the old gray bearded man in the back. He may be able to help you. Good Luck!

JTS

Oh and don't worry about the Governor, as you won't even know it's there until about 8 Thousand RPM
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#3
JTS covered everything fairly well.

All I can add is the FMX never got the credit it deserved for being a tough transmission.  They are a bit heavier due to the cast iron center section.  For that reason most younger folks tinkering with older Fords don't like them.  But, in stock form they can take a lot of abuse and not break.
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#4
I need a clear piece of road to see what she revs out to when held in second.
In the land of "stick shifts", trans shops are very few and far between and trans shops that have dealt with American trans are even rarer ( hens teeth)
The vacuum pipe comes off of the tree on the bulkhead so i might try and get it onto the fitting on the rear of the manifold, I did look today but it's a smaller pipe so needs "adjustment"!
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#5
The only weak spot is you have to adjust the second gear band. It is internal and you can do it at a fluid and filter change. I don't off the top of my head remember the complete procedure. Look up FMX 2nd gear band adjustment. You should find something on it. Once the band is adjusted, and the fluid and filter changed. It will be damn near indestructible. I believe you are correct, that it should have a direct manifold vacumn for the trans. 

JTS
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#6
(09-04-2021, 01:50 PM)JTS71 Mach1 Wrote: The only weak spot is you have to adjust the second gear band. It is internal and you can do it at a fluid and filter change. I don't off the top of my head remember the complete procedure. Look up FMX 2nd gear band adjustment. You should find something on it. Once the band is adjusted, and the fluid and filter changed. It will be damn near indestructible. I believe you are correct, that it should have a direct manifold vacumn for the trans. 

JTS

I changed the fluid and filter a couple of months ago and to be honest would be very very wary about adjusting the band, I tried her yesterday and held 2nd until about 5,500 rpm when I decided "enough was enough" and felt she didn't want to rev any more so I've decided that in the interest of trying to keep her reliable I'll change the vacuum pipe fitting but will live with the way it changes I think.
My problem is I like to drive it as it was intended to be driven without any allowance for it being 50 years old!
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#7
5500 RPM?  Stock Valvetrain?  If so, valves are probably floating or bouncing at that RPM.
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#8
Yeah 5500 rpm might be all she's got to give. Cause we don't really know exactly what you have for cam, and valve train. Can you tell if there are single or dual valve springs? 5500 is probably about max on stock 2 barrel valve train. Stock dual springs about 6500. Hi performance Cam, and Dual racing springs will go way past 8 grand. The governor in the trans shifted to 2nd before it ever ran out of breath, or floated the valves. That's how I know where the "governor" in the trans takes over, and slams it into 2nd gear. Just about 7500 to 8000RPM. Which is way above anything stock. Yeah it was pretty radical back in 1979. But I was having FUN!!!

JTS
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