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Discussion Starter · #1 ·
I have a modified 302 in a 66 Mustang with a rebuilt c-4. Under light accleration, it slides betwee 2nd and 3rd. Under hard accelration it shifts good and hard and holds thru the 1/4. It also blows fluid in 3rd under long and hard acceleration. Any ideas what is causung this?
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The vacuum modulator controls the 2-3 shift. Ford had a system of color bands on the modulator to signify heavy or light vacuum signal control. Most builders prefer an adjustable modulator. Pull the vacuum hose from the rear of the modulator and inspect the inside of the nipple for a bladed screw. If there is a screw in there, turn it clockwise and see if that makes a difference. If no screw, replace it with an adjustable one.

Blowing fluid usually indicates over full or over heating. If the fluid is blowing out the vent and is foaming, very hot, you need a bigger cooler. Keep blowing hot, foaming trans fluid out the vent and right out onto your hot headers and you will need a fire extinguisher or good comprehensive insurance.
 

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Discussion Starter · #3 ·
Thanks for the reply.

I have not checked the modulator and will do so this weekend. This brings up 2 more issues that you might be familiar with: on rare occasions (not often) the tranny down shifts very easily (too easily) but most of the time it does not. Is this the modulator? I also have a slipping reverse and I have adjusted the reverse band until I am blue in the face but with no results, any ideas?
 
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