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Discussion Starter #1
i have been having a problem with my shifting for a very long time. it will not go past about 4100 rpm's before it shifts into 2nd or 3rd, and this is with the gas pedal all the way down. its annoying because it doesn't even get into the power band. i have to manually shift it through the gears if i want to go to 5000 rpm's

i was just wondering what could cause this problem? how do i fix it?
 

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4100? I am by no means a transmission expert, but I think you are asking a bit much from a stock C4. 5000 is pretty darn close to what a stock non-HiPo 289 can do before the valves start to float. They build racing C4's that will probably do what you want, but I don't think a stock one was designed for that kind of abuse. You could try adjusting the modulator inward and installing a longer pin, but I'm not real confident.
 

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Even with a shift kit I have never had shift that late.
An adjustable modulator or longer rod will firm up and cause it to shift later but not very much.
 

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Problem may be the vacuum modulator like Joe said. I wouldn't think 5000 rpm would be a problem. The A code peak HP is at 4800 rpm. K code peak is at 6000 if I'm not mistaken.
 

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Discussion Starter #5
i am no transmission guy, i dont know what a longer rod refers to and where the vacum modulator is. how hard is it to replace or fix these things? how much $? and also if anyone new of a website that could help me, i would really appreciate it. my c4 has been rebuilt and a little more Heavy duty, it bothers me that i cant get it to stock rpm, let alone the few more rpms it could take now.
 

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A bad modulator will cause late or no shift.
Adjusting the modulator will, no way, raise the shift point by even 1000 RPM. It was not meant to be a wide range adjustment.

The longer rod is used when the modulator is not adjustable. You don't need both a longer rod and an adjustable modulator.

I don't know what you consider stock RPM, but Ford wanted the trannys to shift smooth.

Sounds like you need a new valve body.
What RPM's do you consider stock?
 

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Discussion Starter #7
what i mean by stock is the stock power rpm, that 4400 rpms is what im talking about. i would like to be able to get it up to that.
 

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what i mean by stock is the stock power rpm, that 4400 rpms is what im talking about. i would like to be able to get it up to that.
Has anyone something like a tranny guy driven your car? You're getting lotta opinions from people including me who haven't felt, heard, touched your car.

The C4 is a rugged, dependable auto tranny. When the accelorator is floored, like for passing it should downshift then shift back up a little past the hp peak. With an A code that peak is 4800 rpm. This basic tranny was used for many years into the 80's with 302s.

At least spend a couple $ and have a mechanic (not a quick oil change guy or a tyranny salesman) look it over.
 

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I really don't see where you have a problem that needs fixed. I take it that this a street driven vehicle where you will seldom need the higher rpm shift. For those times you do, how much trouble is it to just shift manually? You can make the tranny do anything, but is that really worth investing the coins? But thats just my opinion, it's your vehicle. Even taking it to the strip on weekends, just shift it yourself.
 

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Discussion Starter #10
thank you Slim, i will do so if i every feel the need to really fix it.

yes, this thing is a goodweather cruiser, which around here hasnt been for a little while. i know i can shift it manually, and i do, and im fine with it. it doesnt bother me at all that it wont rev past 4100, the purpose of the post was to make sure that the tranny isnt broken, to the pont where it can cause more damage. incase i want to sell it when i switch to a 4-speed manual.
 

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I agree with you 67 raging... I usually manually shift my 68 because I think it's cool.
I personally like things on my Stang to work like they should even if I can and do get around it!

Good luck,
Slim
 
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