So, I toasted the clutches this fall finally, right when I got to college. I got my spare C4 rebuilt by the flaky shop back home because I was in a hurry. It's my only transportation. Anyway, they put a shift kit in it and, of course, it shifts like crap. It actually shifts really hard if there's a lot of vacuum, but only then. If I just stand on it with the secondaries open, the thing just roasts. They said that it's normal to have to adjust them, which is slang for, "We only know how to build Chevy trannys, and we didn't know Fords could make any power." I really don't want them fooling with my car. Besides the Vac. modulator, what are the external adjustments on a C4 and does anyone have any tips on how I might do it myself. Does the Tranny have to come out to do it right? Thanks
Ricebasher302, The only external adjustments are the bands and the modulator - if they installed an adjustable one. You can probably make it better if you buy a new "green stripe" modulator and use an 8d nail to make a new pin that is 1 5/8" long. Install the modulator and pin after removing the one that is in it now. If the C4 still shifts sloppy then you will have to modify the valve body to change it, I would recommend a 47-2 for 67-69 C4 or 40-2 for 70 and later C4s, The Kits are made by TransGo and are available at some parts houses and transmission shops.
Okay, but i was under the impression that adjusting the rod in the modulator had more effect on shift points than it does on shift firmness. Am I wrong? I hope so, because I can do the things you've mentioned. Thanks!
Shift timing and firmness are related in the C4. The modulator controls a pressure that resists the movement of the shift valve but it also affects the amount of pressure holding the clutches. In conjunction with the "kick-down" linkage pressure is increased to hold more pressure on the line pressure. Typically the pressure will decrease with more vacuum and less throttle. I am concerned that you may have a wrong modulator in your tranny. If the modulator has two lines to it use only the larger of the two and connect it on the rear of the green strip modulator (which only has one connection). The pin increases modulator pressure to near maximum over the entire range of possible vacuum signals. You can adjust the "kick-down" linkage with the engine off. hold the carburetor linkage wide open. (you may need help) With the carb held wide open, push the down shift rod towards the transmission as far as it will go. You should have no more than 1/16" gap between the adjusting screw and the throttle linkage. As long as there is some gap but not more than 1/16 inch you are ok. Those are the only external adjustments that should be made. I don't recommend that you adjust the modulator when using the green stripe one and the long pin. Unless you have a turbo or other blower it should work fine. If it doesn't then the TransGo kit is recommended. (The TransGo kit will have the long pin and a shorter one and they recommend the green stripe modulator) Pay close attension to the mods and check each one off as you do it. It takes a couple of hours to install the kit so a weekend would be a good time to get it done.
what if your not using kick down linkage? still a green stripe and a 8d nail? not to interrupt, but just curious.
Wagesofsin, If you are not using your kick-down linkage then you should shift manually - you might as well put in a manual valve body. When you take the C4 out of "Drive" you raise the operating pressure to its maximum. (for what ever RPM you are at) As soon as you put it back into drive the pressure drops to the lowest pressure for that RPM. Essentially you are going down the road with the pressure in your transmission set for idle. Any load is more than the pressure is meant to take. You may never notice that your C4 is slipping until you have to pull it out and you wonder why the steels are all blew and the paper is worn off the clutch lined plates. If the Kick-down" linkage wasn't necessary then Ford wouldn't have spent the $14 per C4 to have it there. (It would have saved them over $20 million each year of production) I can't say it enough - Unless you have a manual valve body use the kick-down linkage. The same green stripe modulator and a 1/58" pin are used in all but some truck transmissions for performance. You can make the pin from an 8d nail by rounding the sharp end and then cut it 1 5/8" long and round the end you cut.
its a strip car paul, just wondering, didnt wanna come off as ignorant, it is a manual v/b. i totally respect your knowledge, and input, thanks for clarifying the function as to the pressure, thats what i was lookin for.
Wagesofsin, For your strip car (if you use a vacuum modulator) you can make it shift at the maximum shift point by disconnecting the modulator vacuum line and plugging it. (be sure to leave the modulator port open) The governor will still shift the car but it won't be fighting the modulator to do it. Yours, having a manual valve probably doesn't use a modulator. (most don't)
Paul S, Thanks for all your knowledge. I actually am not using a kickdown lever. My car was a 3 speed 6 cyl, but when I put my 302 in, I just stuffed a C4 in so I wouldn't grenade my 3 speed. My dad's early bronco isn't using a kickdown lever either and it shifts beautifully. That's not to say you're wrong, but I just figured it could be done. (Do I remember having to cut the kickdown linkage off to put my B&M shifter on?) My trans. shifts exactly the same whether I'm shifting manually, or in drive. 1st to 2nd is especially bad. However, the minute my vacuum comes up, like if I let the rpm level off or if I quickly snap the throttle closed before shifting, it shifts like mad. I'm starting to make a little sense with all your help, but if this gives you a better idea, feel free to keep sharing the wealth. You're an immense help to a poor gearhead college student.
It may feel like it shifts the same whether you are in drive or manually shifting but if you hook a gauge to the test port you would see more pressure (about a 30% increase) when you are shifting manually. I have provided all the help I can. I hope it helps you solve the problem. There are kits to connect the "Kick-down" linkage with after market shifter kits.
