Best C4 question

[brianproctorla]

I am doing a write-up on the ford C4,C6, and C6.
I am trying to determing which is the best case to choose.
I know that 1970+ cases feature a 24/26 or 26/26 splined .839 input shaft.
This case also bolts to the case instead of the front pump which makes it the best C4.

I also read that that certain C4's have dipstick that goes to the pan. These C4's have a 12 inch torque converter instead of an 11" inch.

Is the larger torque converter preferable to the 11"? Did this converter come with c4's prior to and post 1970?

 

[brianproctorla]

The pan fed C4 uses a 164 tooth flexplate and the case fed uses a 157 toothed flexplate. The 164 toothed flexplate can only be used in the pan fed tranny. Each flexplate can be balanced to match the engine. I believe a bigger clutch can be used with the pan fed

 

[brianj5600]

Where is the write up going to be?

 

[D.Hearne]

According to my transmission guy, there is a 164 tooth bell for the case fill transmission. Or was it a 157 for the pan fill ? The pan fill has more clutches and a better "H" servo for the 2-3 shift. The 24 spline input was in the pre 70 C-4's.

 

[brianproctorla]

Thanks. That makes a lot of sense. The Pan fill C4's were for heavily duty applications and therefore should be built a little tougher.
What about the C5 case? I've heard the case is stronger than the C4, but the internals were not as tough. Same basic internals, less quality.
I know the locking torque converter weakens the case as it generates more heat. Would a C5, built as a C4 case be stronger than a C4?

I will let you know of the site as soon as I launch it. I am just compiling data for the C4,C5,C6, and trying to determine strengths and weaknesses

 

[D.Hearne]

I'd have to ask him, as far as I know the cases are interchangeable, or at least you can use C-4 internal parts in a C-5. The Pan fill C-4 is also refered to as a C-5 in some places.

 

[brianproctorla]

From what I've gathered, the C5 case is a bit stronger and has better oiling circuitry. This oiling improvement can be performed on a c4 by drilling a hole to allow better flow to the number 9 thrust bearing. The internals are not as strong as the C4. The c5 has a locking converter that will ad an extra 1/2 gear. This can add more head and decrease strength, so performane builds generally swap out the locking converter.
The bellhousing is the widest c4 and the case vents through the tailhousing.

 

[D.Hearne]

The C-5 bell isn't wider but it is deeper (or longer) making the overall length of the transmission 1" or so longer.

 

[brianproctorla]

That's right. It is actually longer, not wider to account for the locking torque converter. The bellhousing won't work with a 200 ci cyl that is from 1964-1979ish.
It has a partial windsor bolt pattern which is a blend of two bolt patterns.

 

[brianproctorla]

I just picked up a C4 from a 78 thunderbird with the 429/460 bolt pattern. Unfortunately after I cleaned the bellhousing, I noticed the webbing was cracked on one bolt hole and there were small cracks near the crown of the starter. These cracks did not go all the way through the case. Is this repairable? I do not need the bellhousing, but I had planned on selling it

 

[D.Hearne]

If it's aluminum, it can be welded. Sure it's a C-4 and not an FMX ?

 

[brianproctorla]

That model car did come with a fmx, c4 and C6. I could see that the bellhousing was separate , which ruled out the C6. The easiest way, I believe to tell a C4 from an FMX, is the cast iron case (not bellhousing or tailhousing). When you are at the junkyard, it's hard to tell iron from copper as the trans will be covered in crud. If I was smarter, I should have brought a small magnet to press against the case. If it sticks, it is an FMX.

My transmission is a C4, but I have yet to clean off the case. I hope I don't get any more surprises when I get the mud and oil off.

 

[brianproctorla]

I meant iron from aluminum. The cleaning fumes must have gotten to me

 

[D.Hearne]

You can tell them apart just by looking at the bellhousing itself. The FMX bolts on like a manual trans bell, four bolts on the outside, the upper bolts are closer together than the bottom two. The C-4's are inside the bell.

 

[brianproctorla]

i was not aware of that. That's a great observation.

 

[D.Hearne]

The pan on the FMX is also easy to Id. It's rectangular, wider than it is longer. Also a bit deeper than a C-4 pan.