My '66 F100, 240 with a C-4 has a problem. Finally got the carb and timing adjusted out and took it for a long (15 mile) cruise today. My problem is the tranny won't shift into 3rd gear. I brought it back to the house, and checked the linkage, everything seems alright. Checked the kickdown, and seemed to be too tight, so adjusted it so it would actuate at all, in case that was the problem. Still won't shift but from 1st to 2nd. The PO told me the engine has less than 5k on it, and then he had the tranny built after that. He's not very mechanical at all, couldn't tell me much else except that he kept gas in it, and drove it. It has been sitting for the past year or so before I aquired it. I once had a '68 Cougar that I had pulled the engine and tranny to build the engine. Rolled the tranny over to change the filter and gasket without thinking, and had the same problem with it. A tranny guy I knew at the time said to get it to about 60 in 2nd gear, and the slam it into 3rd. I did that the second time, and it worked from there on out. Stuck checkball in the valvebody. Can't get this truck to do that. Any suggestions? Thanks, Brian

 

Should be a vacuum line going from your carb or intake(not sure, mines on the intake on my six)to the modulator on your tranny. Is it hooked up? If it's not, that will prevent an upshift.

 

Checked it today, and the vacuum is fine all the way to the modulator. It's been a long time since I owned anything with a c-4 in it, but if the modulator goes bad, won't it cause this problem? I know I've seen others before that would go bad and cause it to suck trans fluid back up to the intake. So little that you can't tell it in the exhaust. That was a fun one to diagnose though. Not a drip or seep on the entire tranny, but kept losing fluid. Learned from that one quick though. Any more info guys? Something simple I'm overlooking for sure. Thanks, Brian

 

Also, does anyone know which modulator this tranny should have. The blue or white stripe. The current one is blue. Thanks.. Brian

 

C4AZ-7A377-B .. Vacuum Throttle Valve Diaphram aka Modulator Valve (Motorcraft TM-2) Still available from Ford.

Fits: ALL 1964/71 and some 1972 Ford cars & trucks (regardless of engine size) with the C4 transmission.

The color band is white, and there may be a white dye spot on the module.

From FTE sponsor DIRECT FORD PARTS online parts locator:

Ford suggested retail price $41.18 / FTE Member Net Price $21.83
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The blue modulator valve (D7BZ-7A377-A - M/C TM-41) is incorrect!

It was used as an altitude compensating diaphram on some 1977/78 Granada's/Mustang II's and Mavericks.

 

Try adjusting the modulator by backing the screw out a turn at a time and see if the condition changes at all.

 

I hope that all of you had a very Merry Christmas. Enjoyed the day myself with family and my 2 boys celebrating. That's what Christmas is all about. Anyway, I'll try adjusting the screw first to see if that one works at all, and will probably wind up replacing it anyway to make sure. Looks like, with further inspection of the rubber hose, that it might be sucking trans fluid. Thanks ND for the part # of the correct one. Again, hope everyone had a very blessed day, and that a great New Year is in your future. Brian

 

Tried adjusting the blue stripe one, it was already about all the way in from someone previous. No difference. I replaced it with the correct one, and tried that. Still no 3rd gear. Adjusted back and forth, but just prolongs or shortens the shift to 2nd. Any more info or ideas would be greatly appreciated. Thanks, Brian

 

back off on the kickdown linkage some more just to makesure it isn't pulling too far. check the vacuum at the modulator with a gauge. The modulator has a pin in the hole that fits in the tranny. that length is critical. someone may have ground it down.

 

OK, I now feel like a dummy. Didn't know that my c-4 was a green dot version. Shift indicator and dial missing a long time ago apparently. Got the truck to my work finally, and pulled the pan and valvebody, after trying unsuccessfully many times to get it to shift while on the rack. Still would work right. Disassembled the VB, and you cannot imagine how much crud was stuck to the separator plate. Pulled all the valves and cleaned thoroughly, put all back together, and tried it again. Works find now. Just have to adjust the modulator with a little more playing to make it right, since it's way out now. Thanks so much fellas. Aren't these slicks so much fun???
Brian