C4 Trans not shifting when Cold - Ford Muscle Forums : Ford Muscle Cars Tech Forum
 
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post #1 of 8 (permalink) Old 10-30-2016, 02:10 PM Thread Starter
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C4 Trans not shifting when Cold

Hello All,

Hey everyone,

So I got my car back a few days ago from the shop for an engine repair and I noticed some issues with my c4. When cold, it doesn't want to upshift when in Drive. It does go in reverse and 1-2 are fine when shifting manually, but when I go into drive it over revs, or seems like it goes back to 1st.

When the car is all warmed up the car can shift through all 3 gears, the shift points are much wider now as I assume they adjusted the shift points but the shop owner is saying they didn't touch anything.

When Cold, I check the fluid level and it shows little to no fluid, when warm the fluid is at level.

the thing shifted Great before I dropped it off though I did have a 2-1 down shift "Clunk", I spoke with the owner of the shop to look into this.

I checked vacuum pressure on the modulator, and I am getting pressure. Any suggestions? could it be incorrect fluid? or stuck relief valve? Its push-in modulator and the c4 was built by Performance automatic a few years back its the super streeter from PA Automatic.


****update so I spoke with the mechanic that worked on my car, he did adjust the shift points and added some fluid. Before I send the car back I would like some suggestions as I would like to look into this myself. before handing it off to them.
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post #2 of 8 (permalink) Old 10-31-2016, 01:07 PM
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Re: C4 Trans not shifting when Cold

Just wondering how he adjusted the shift points.

1966 Falcon, 347 stroker and C-4
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post #3 of 8 (permalink) Old 10-31-2016, 03:05 PM Thread Starter
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Re: C4 Trans not shifting when Cold

Quote:
Originally Posted by falconfred View Post
Just wondering how he adjusted the shift points.
from what he told me I have an adjustable "pushing" Vacuum modulator

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post #4 of 8 (permalink) Old 10-31-2016, 03:06 PM Thread Starter
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Re: C4 Trans not shifting when Cold

Quote:
Originally Posted by rwcstang View Post
from what he told me I have an adjustable "pushing" Vacuum modulator
Correction*** "Push In"

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post #5 of 8 (permalink) Old 11-01-2016, 02:47 AM
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Re: C4 Trans not shifting when Cold

Well have a look where the screw adjuster is now . Back it out 1 turn at a time . Just keep a track of where it was originally so you can go back if needed
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post #6 of 8 (permalink) Old 11-01-2016, 07:05 AM
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Re: C4 Trans not shifting when Cold

If I recall correctly backing out the screw legenthens the shift pattern. A lot of c4s I've run across with an adjustable modulator the screw was missing probably trying to correct a shift concern. The idea of an adjustable modulator was to be able to make minor adjustment to the shift point without removing the modulator and replacing the pin that fits into it. Ford offered shorter or longer pins depending on which way you needed to go. Shorter pin, shorter shifts, longer pin, longer shifts. On cars without an adjustable one, we use to just make a pin for it. And while your at it, make sure the pin is even there. Had cars that had the modulator replaced and the pin would fall out into the drain pan when the guy went to replace. If the guy didn't notice it and put it together without it, it would cause all kinds of problems.
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post #7 of 8 (permalink) Old 11-01-2016, 12:12 PM
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Re: C4 Trans not shifting when Cold

I agree with lowrider, I think the pin may have fallen out.
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post #8 of 8 (permalink) Old 11-02-2016, 03:36 AM
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Re: C4 Trans not shifting when Cold

Also the pin length must be checked before any modulator adjustment. On a push in type it must at least have a slight preload
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