V8 in front of a I6 C4

Hack · Dec 5, 2005

I recently swapped a '89 302 into my 1970 vert. Once I complete the job and get it running, I will have the original C4 behind it for a while. Eventually I plan on going to a T5, but that will be down the road a ways.

Anyway, my question is: can I buy some parts to upgrade my C4 to make it strong enough to easily run behind a mild 302? Does it even need to be upgraded? How easy/difficult is this to do? Is it a good idea?

Thanks!

LMan · Dec 5, 2005

I think a 250-Six C4 will handle normal driving behind a 302. The six prolly has the V8 beat in low-end torque, anyway.

Truth be told, its prolly the same C4 from the factory.

brianj5600 · Dec 5, 2005

I6 c4's are different. They have fewer clutches and smaller servo's. I would have a backup plan and keep a friend's number close. I can't answer if it will hold up, but I know they are weaker.

302 coupe · Dec 5, 2005

it will work for usual driving, but if you beat on it, it won't last long. Been there, done that. If you give it a try, you'll need a V8 bellhousing and torque converter. Make sure to count the splines on the input shaft so you get the right converter.

thehueypilot · Dec 5, 2005

I used mine for about a year and raced it one season with no issues behind a mild 351W before switching to an AOD.

Hack · Dec 6, 2005

302 coupe said:
it will work for usual driving, but if you beat on it, it won't last long. Been there, done that. If you give it a try, you'll need a V8 bellhousing and torque converter. Make sure to count the splines on the input shaft so you get the right converter.

Umm, I'm not sure what you're talking about here. Perhaps the early Mustangs are different than the '70s?

My C4 in my '70 bolted right up to my 1989 roller 302. I didn't have to change the bellhousing or torque converter.

Of course I did have to buy a new flexplate with 157 teeth and 50 oz balance.

5.0ina66 · Dec 6, 2005

Hack said:
Umm, I'm not sure what you're talking about here. Perhaps the early Mustangs are different than the '70s?

My C4 in my '70 bolted right up to my 1989 roller 302. I didn't have to change the bellhousing or torque converter.

Yep, 250 I6 cars ard Different with a capital D! I wouldn't be surprised if it's the same as a V8 C4; after all, 250ci cars had the full V8 suspension, and the 250 is SBF bolt pattern.
HTH
--Kyle

brianj5600 · Dec 6, 2005

brianj5600 said:
I6 c4's are different. They have fewer clutches and smaller servo's.

Do not ASSUME. The servo is obviously smaller w/o a doubt. Some were built with only 3 clutches in both drums. V8's had 4 or 5 clutches.

302 coupe · Dec 7, 2005

Hack said:
Umm, I'm not sure what you're talking about here. Perhaps the early Mustangs are different than the '70s?

My C4 in my '70 bolted right up to my 1989 roller 302. I didn't have to change the bellhousing or torque converter.

Of course I did have to buy a new flexplate with 157 teeth and 50 oz balance.

I forgot about 250's having the bigger bolt pattern, sorry.

Hack · Dec 7, 2005

brianj5600 said:
Do not ASSUME. The servo is obviously smaller w/o a doubt. Some were built with only 3 clutches in both drums. V8's had 4 or 5 clutches.

I broke down and looked in my 1970 Ford Service Manual. It describes two C4 transmissions. C4 and C4S. I guess the C4S had to be manually shifted. It looks to me as though the C4 only went behind I6 engines in 1970. Is that true?

As far as I can tell from the manual, there's only one set of C4 parts available in 1970 Ford cars. The manual does not describe 2 different models of C4s with different numbers of clutches or different servos. Possibly this is a mistake, but I would tend to trust the manual.

Anyone here know whether there is a difference between a 1970 C4 from a 250 I6 car and a C4 that went behind a V8? What years did the C4 go behind the V8? Maybe I can talk to my local auto parts store or transmission shop about this. They could tell me what part numbers are used for rebuild kits, servos, etc. What do you guys think?

brianj5600 · Dec 7, 2005

Can you post a pic of the front servo? I may have to eat my words. '70 models may be different than earlier ones. They made some changes that year. Is there a letter on the front servo cover?

Hack · Dec 7, 2005

brianj5600 said:
Can you post a pic of the front servo? I may have to eat my words. '70 models may be different than earlier ones. They made some changes that year. Is there a letter on the front servo cover?

I think I have to eat my words instead. I was looking in my manual trying to figure out what a servo is and where it is on the trans, and I found a table on page 17-02-21 of my manual listing a V8 servo and an I6 servo. So, now I believe that you are absolutely correct.

According to my manual, the trans in my car should have the letter B on the servo, whereas the 302 would have an A and the 351 an R. They all appear to use the same spring, but different covers. From the diagram it looks to me that the I6 cover is thicker.

Since I missed that big item, I looked through again trying to find other differences listed but didn't see any.

Edit: I finally found on page 17-02-41 where the manual lists different numbers of clutches for the V8 and I6 models. It also lists different booster and accumulator valves. So does that mean that I would have to change essentially the entire guts to make it into a V8 model?
I wonder if it makes any sense for me to change out the servo and leave everything else alone? Could someone please explain to me the function of the servo?

JB66 · Dec 7, 2005

from the 1970 car service specifications book...
10 different models of C4 for the 250, 302 engines
1. PEA-M2, PEA-N2, PEE-V2 for 302-2v w/12" converter
2. PEE-AD1, PEE-AE1, PEE-AF1 for 250 w/11 1/4" converter
3. PEE-M1, PEE-V1, PEE-AC1, PEE-AH1 for 302-2v w/11 1/4" converter
#'s 2 & 3 use the same DOOP-7902-A converter
the PEE's and PEA's all use 4&5 plates in the forward clutch and 4&4 plates in the reverse clutch.
the booster valve and accumlator valve springs vary slightly.

mdjay · Dec 8, 2005

I wouldn't worry about it too much Hack...

I ran one behind a mildly modified v8 for years without any problems.

Like 302 said, if you beat on it, power brake it etc, you're gonna create problems. If you just drive and enjoy, you should be fine...

Hack · Dec 9, 2005

Thank you all for the helpful advice.

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