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6 cylinder C4 vs V8 C4 differences?

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Hello everyone, hope things are going well.

Today i have a question out of pure curiosity, so ive come to the mustang database of wisdom.

What are the differences between the 6 cylinder c4 and the 289-302 c4?

Im planning on possibly switching to a v8 down the road, and I know the converters and flexplates and bellhousings are different, but if i switch all of those out onto a l6 C4, would it be okay to support a 302?

cheers!:cheers:
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Having just been into a early C4 on my sons car I know the the servo pistons are different and the forward clutch housing is different between the 6 cylinder and V8's. The machined groove for the snap ring on the interior of the clutch housing is further up on the V8's to allow for more frictions and steels. i'm sure that there are other differences as well.
 

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I recommend you switch. To a V8 C4 now and then you'll be all set when you move up.
 

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The gearing is different between the I6 C4 and the V8 C4, Yet the difference is not major enough to cause outrageous results. I have successfully swapped I6 C4's into V8 cars and you would not even notice the difference.. and vice versa, I have swapped V8 C4's into I6 cars. You just change the bellhousings and flexplates.

If you're thinking of doing a swap such as this for normal driving. Breathe easy. It's an easy swap, and you don't have to worry about it.

"but if i switch all of those out onto a l6 C4, would it be okay to support a 302?" - For normal driving Yes, If you're hitting the dragstrip every Saturday night, Then No.

:eek:)

Tony K.
 

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I am doing the I6 to V8 swap and plan on rebuilding my I6 C4 to the V8 standards also. From the BadShoe video series, I have learned that yes, the bell housing and flywheel are different, the clutch packs have an extra clutch in them and the servo is different. Ken with BadShoe is great at about responding to questions, will ask him about the gearing. IMOH, yea......you can run an I6 C4 on a V8, but if it is a tired C4 it will wear out fast due to the condition of the clutches being worn and not up to the task of the V8 torque/power. Yea, a freshly rebuilt C4 will last a little longer, but if you have a lead foot and are hard on the engine/transmission, again.......do to having 1 less clutch in the packs, it will start slipping/wearing out faster. Again.....talking to transmission shops and watching/e mailing Ken, yes.....an I6 C4 can easily be built to V8 C4 specs.

Why am I doing it and not just going with a V8 C4? 1. Satisfaction that I am going to rebuild my transmission myself and am confident with Kens assistance if I have any questions, I will get it right and 2. It is the original transmission to the car, so even though I am replacing the engine with a 289, I want to keep as many origional parts/components on/in the car as I can.

If you search old post, there are many questions like this. Once I actually do this, I plan on creating a post showing the differences . I actually picked up for free, an old 65 V8 C4 that I was originally going to rebuild to put in the car. I may disassemble it at the same time, document the differences (clutches etc) as examples for my future posting.
 

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Discussion Starter · #7 ·
thanks for everyones reply! and sean i like your approach, i might consider just rebuilding this one. Ill have to wait and see
 

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Well I learned the hard way there are 2 different sized torque converter splines. I was not on this forum when I put my 289 in & was never a Ford guy. I asked a bunch of different people & done a lot of googling every one said the six trans will be fine just use the V8 converter. I had a friend over helping me & he put the converter in & it slid right in. It was all good until we started it & put it in gear. :bitch: That is when I read more and learned about the different sized splines. GRRR Well it ended up with a V8 trans in it a couple days later.
 

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Well I learned the hard way there are 2 different sized torque converter splines. I was not on this forum when I put my 289 in & was never a Ford guy. I asked a bunch of different people & done a lot of googling every one said the six trans will be fine just use the V8 converter. I had a friend over helping me & he put the converter in & it slid right in. It was all good until we started it & put it in gear. :bitch: That is when I read more and learned about the different sized splines. GRRR Well it ended up with a V8 trans in it a couple days later.
the difference is TQ splines has to do with the year of the transmission rather than what it came behind. you cant use a 1970 TQ in a 1969 transmission.

as for the rest, the clutch packs have one less clutch in them, the servos tend to be a bit smaller, etc. you can add back the one clutch in each clutch pack though, and you can change to the larger servo pistons as well in some instances.

but even if you just rebuild what you have and upgrade the better components, ie better clutch packs, the six cylinder C4 will handle a mild 302 in normal day to day driving, and even the occasional ragging at the strip(that means a couple times a year, not every other week).
 

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the difference is TQ splines has to do with the year of the transmission rather than what it came behind. you cant use a 1970 TQ in a 1969 transmission.

as for the rest, the clutch packs have one less clutch in them, the servos tend to be a bit smaller, etc. you can add back the one clutch in each clutch pack though, and you can change to the larger servo pistons as well in some instances.

but even if you just rebuild what you have and upgrade the better components, ie better clutch packs, the six cylinder C4 will handle a mild 302 in normal day to day driving, and even the occasional ragging at the strip(that means a couple times a year, not every other week).
Both cars I pulled apart were 68 models. I know my car was original & the other one was supposed to be I know the tags on the rear end & motor were but maybe some one had changed the trans along the way. Mine was 24 spline & the other was 26. Any way now that I learned the hard way I will always check if I do any more Fords.
 

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Both cars I pulled apart were 68 models. I know my car was original & the other one was supposed to be I know the tags on the rear end & motor were but maybe some one had changed the trans along the way. Mine was 24 spline & the other was 26. Any way now that I learned the hard way I will always check if I do any more Fords.
its not the year of the car you need to look at, but the year of the transmission. up to 1969 all C4 transmission had 24 splines on the input shaft. it didnt matter if it was a V8 or six cylinder trans. starting in 1970 ford went to the 26 spline transmission input shaft on the C4s. chances are the someone did change the transmission along they way. personally i never look at the bolt on tag anymore, they can be easily swapped. rather look at the casting numbers instead, especially the date codes as that will give you more accurate information.

another possibility is that perhaps the case was original, but someone had the trans rebuilt, and upgraded to 1970+ internals.
 
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