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Old 10-07-2011, 10:53 AM
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Early shifts on transplanted 1963 Ford transmission

Working on a 34 Ford with flathead, and 1963 Ford automatic.

The transmission has 11 bolt pan, but has a C3 year for casting number, being 1963.

My question is this:
It shifts early 5-8 mph to second, 20 mph for 3rd. We thought it might be the modulator valve adjustment.

We have adjusted the screw in 5 turns from where it was on the modulator with no change. Of course we have no idea if it was in the right spot to begin with.

So we removed the vacuum from the modulator to see if we were thinking right, thinking it would shift a lot later and hard, but the results were the same, early shifts.

Any suggestions? The cable for kickdowns is not hooked up, thinking this is just for kickdowns.

Any suggestions or corrections to our thinking?

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Old 10-07-2011, 02:23 PM
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Quote:
Originally Posted by grobb284
Working on a 34 Ford with flathead, and 1963 Ford automatic.

The transmission has 11 bolt pan, but has a C3 year for casting number, being 1963.

My question is this:
It shifts early 5-8 mph to second, 20 mph for 3rd. We thought it might be the modulator valve adjustment.

We have adjusted the screw in 5 turns from where it was on the modulator with no change. Of course we have no idea if it was in the right spot to begin with.

So we removed the vacuum from the modulator to see if we were thinking right, thinking it would shift a lot later and hard, but the results were the same, early shifts.

Any suggestions? The cable for kickdowns is not hooked up, thinking this is just for kickdowns.

Any suggestions or corrections to our thinking?
You assumptions are probably correct. Your modulator system is the culprit. Do two things: first reach in with a pencil magnet and see if you can extract the modulator valve out of the case. It should be free and come out easily. Secondly, put a vacuum source on the modulator and a small screwdriver in the hole on the transmission side of the modulator. We are trying to determine if the modulator is actually working. If you don't see movement as vac is applied and removed, replace the modulator. You are correct about the kickdown. It simply overrides governor pressure to force a downshift by changing pressure on the shift valves making them move to the prior gear position.
You say that it is a 63 transmission? Is the case cast iron or aluminum?
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Old 10-08-2011, 07:33 PM
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also check the modulator pin it goes between the valve and modulator
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Old 10-09-2011, 02:25 PM
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Quote:
Originally Posted by anglia427
also check the modulator pin it goes between the valve and modulator
It was missing the modulator pin.

Any idea how long it needs to be? This is the push-in style. I made a pin 1 5/8 long. It shifts harder now, but not at a higher speed.
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Old 10-09-2011, 06:19 PM
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grobb284,

you mention a flathead Ford engine. Is this a Flat-O-Matic conversion to a C4 transmission?

A C4 with a push in modulator would be a 1970 or later transmission as I recall.

Do you have the TV linkage from the carb to the transmission hooked up? This is the inner threaded shaft at the shift linkage location.

the only measurement on the modulator pin I have is 1.618 long for an OEM pin

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