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Old 03-10-2011, 07:31 AM
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C4 transmission help

Hey guys, this is my first post. I need major help. I bought a rebuilt C4, it set about a year before I used it. It will not shift on its own, when I shift it manually, it shifts first to second then when I go in drive it goes back to low. The valve body had stuck valves, fixed them still same thing. I checked modulator valve for the pin, it's in. Checked governor, it's not stuck. It has a good vacuum on modulator. I checked shift pattern on shifter and transmission. Revers works fine, low and second is fine. It has a shift kit installed, I don't know what kind. Any help is greatly appreciated.

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Old 03-10-2011, 08:52 AM
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First post - welcome aboard!!

If someone screwed up with drilling the two holes in the valve plate, forgot a ball or installed a spring in the wrong place when they did the shift kit, your shifts will be incorrect. Find out what kit was used, pull that valve out and try to find the instruction sheet. If that's correct, we can go from there.

Also - is the servo, right hand side assembled correctly? Then under the filter there is a spring and pin under a tab that needs to be there for correct oil flow.

I always suspect something is wrong with a rebuilt so I usually at least partially disassemble if for no other reason but to make sure all of the parts are there. Sticky spool valves on only a 1 year old rebuild would be cause for me to worry even more as these should have had enough ATF or at least some assembly Vaseline to keep them free. The one I currently have in my '31 sat virtually empty for 4 years and works just fine (except for a @#$% drip I cannot find)

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Old 03-10-2011, 09:04 AM
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I don't remember seeing anything under the filter. As for what kit, I will have to try to find out. I bought it from someone who had it built for a drag car. Also the screw in the modulator is all the way out, Would that affect it? Thanks for the help.
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Old 03-10-2011, 10:27 AM
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Quote:
Originally Posted by rawdogn
I don't remember seeing anything under the filter. As for what kit, I will have to try to find out. I bought it from someone who had it built for a drag car. Also the screw in the modulator is all the way out, Would that affect it? Thanks for the help.

Here's a real nicely done article about C4's:http://www.mustangandfords.com/techa...ion/index.html

The modulator - might be junk. You only want to go 2-3 turns from factory setting. Also, take a look at the photo of the servo valve and how it controls the the band applications through intermediate gear. Clutches - high - all controlled by the valve body and how someone assembled it after "mods" That pin - see photo 32, between the guys two fingers there is a tab - and under it is a pin and spring. Double click on any of the photos to see a list.

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Old 03-10-2011, 10:34 AM
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Quote:
Originally Posted by rawdogn
Hey guys, this is my first post. I need major help. I bought a rebuilt C4, it set about a year before I used it. It will not shift on its own, when I shift it manually, it shifts first to second then when I go in drive it goes back to low. The valve body had stuck valves, fixed them still same thing. I checked modulator valve for the pin, it's in. Checked governor, it's not stuck. It has a good vacuum on modulator. I checked shift pattern on shifter and transmission. Revers works fine, low and second is fine. It has a shift kit installed, I don't know what kind. Any help is greatly appreciated.
What year is the tranny? When you drive off in "D", what happens?

According to "PaulS" on another board, your problem may be:

Quote:
Make sure your down-shift rod/cable is working freely.
The only other place to look is in the valve body or governor.
AND:
Quote:
If you have all gears but third then there is a problem in the seals of the direct drum, sticky valve body, 2-3 shift valve, or governor.
If you can take it for a drive and start in manual low, shift to second about 15 mph and then into 3rd at 30 and see if it shifts that way. Then using drive use moderate throttle and see where it shifts into 2nd and then 3rd. If it won't shift into third then take it someplace where you can get your speed up to about 75 and see if it shifts at 75 or before. It might be that the vacuum modulator pin is jammed into the valve and not letting it move with the vacuum. Try pulling the modulator and re-installing it making sure to get the pin in place in the hole in the valve - that valve might be in backwards.
Those are my thoughts off the top of my head. I hope it helps. AND: Not shifting into high could be a stuck governor, bad vacuum modulator or sticking valves in the valve body - 2-3 shift valve, modulator valve or a warped valve body.
GOVERNOR:
Quote:
You should be using a "Green stripe" modulator with a modulator pin that is 1.625" (1 5/8") long (If your modulator screws in then you will want to use the White stripe modulator). You might have a stuck governor - you can get at it by removing the tail housing and pulling the four small bolts that hold it on. Disassemble (keep track of how the valves, springs and shim come out of it) polish each valve with 600 grit emery paper and lube with some Vaseline before installation. They should move freely in their bores. Clean the small thimble filter and reinstall it in the governor mounting block before remounting the governor on the tail shaft. Use a new gasket on the tail housing and put a thin film of loctite or permatex 518 on both sides.
VALVE BODY LINKAGE:
Quote:
have the manual valve lined up with the pin on the "rooster comb". That pin has to go in the first groove in the manual valve spool. The down shift lever has to tuck into the space behind the kick-down valve. To make it easier on yourself when you install the valve body use a couple pieces of threaded rod (1/4" NC x 4" long and a couple of nuts to hold the valve body in place while you line up the two levers. Check them often as you start to install the bolts. It can be a real pain to get everything lined up when you are under the transmission and oil is dripping down your arms but it can be done.
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Old 03-10-2011, 01:03 PM
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I don't have kick down hooked up, but it is moving free. I'm not sure what year it is. I have it on a rack and run it up about 60mph, still no shift. It will not shift at all if I leave it in drive.
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Old 03-10-2011, 04:06 PM
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Quote:
Originally Posted by rawdogn
It will not shift at all if I leave it in drive.
Does that mean the wheels turn and it stays in first, or no wheels turning in drive, period- like it is in neutral?
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Old 03-10-2011, 05:56 PM
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It shifts back to low gear.
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Old 03-11-2011, 09:21 PM
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Vintage is important. If this is a trans that was produced prior to 1969, the normal D position is actually 2. The "2" position is D on this type trans. These are called "green dot" transmissions and the valvebody is different. If the trans upshifts in the more normal "2" position, it is a green dot valvebody. Start with the shifter in 2 and see if it shifts.
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Old 03-11-2011, 09:33 PM
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Still no shift.
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Old 03-12-2011, 07:16 AM
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Time for a trans shop with early transmission experience. You are missing something.....
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Old 03-14-2011, 05:11 PM
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OK guys, I had time to check it today. I do have a green dot valve body. Should I try to fix this transmission, or buy another one?
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Old 03-14-2011, 08:19 PM
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Is your intent to have this trans work as a stock type unit or street/strip unit?
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Old 03-14-2011, 08:27 PM
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I intend to put it in gear and drive. lol
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Old 03-15-2011, 03:33 PM
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the green dot valve body can be replaced with a 1967 , 68 or 69 valve body for regular shift pattern PRNDSL ... place shifter in "D" and trans upshifts and downshifts in all 3 gears.

this valve has the shifter linkage detents in the valve body as needed
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