Technical Why not the C4? TH350 vs C4

When talking about swapping to a more modern transmission, it seems almost universally the first transmission that comes up is the TH350. In fact, GM Turbo Hydramatics seem almost universally more popular than offerings by Ford or Chrysler. Admittedly, GM makes some good transmissions. The Powerglide in stock form made for reliable cruising and modified made for a great drag transmission. The TH400 is tough and strong and well suited for heavy duty applications. The 700R4 is the path of least resistance into automatic overdrives and doesn't require a computer to run.

And the TH350 seems to be the gold standard for ease of installation and operation, needing only a vacuum source to function. They shift nice, gear ratios are suited for a wide array of uses, and they can take a decent beating. They're also the second half of the 350/350 combo that has dominated rodding for the past 40 years. It's a proven formula.

The intent of this thread is not to say "Why the TH350?" Instead, I want to focus on the positives of the C4. Having owned both, I'll start.

-I can't speak for the upper limits of the C4s capabilities but probably 90% of us do not have drivetrains that are going to turn a properly functioning automatic to minced meat with raw horsepower, outside of abusing driving habits. The C4 seems to be comparable to the TH350 in terms of durability.
-In modified form, the C4 seems to be a very sturdy transmission, often used in SBF and Mustang drag applications.
-Gear ratios are substantially similar.
-Neither requires a TV linkage and is able to operate properly with a vacuum source for the modulator.
-Performance parts are readily available and not terribly expensive.
-The C4 is physically smaller than the TH350, and would be able to fit in a more confined space.
-The C4 has a completely removable bell housing that could, in theory, be utilized for a number of applications where the Chevy bolt pattern is too big, or where there is no need for an integrated bell on the transmission case, such as Early Hemi, Early Cadillac and so on, where there is a deep skirt on the block.
-The SBF/C4 seems to be the lesser used, but still very effective, alternative to the 350/350. Which is still a proven formula.

So with all of that said, why not use a C4?

 

Good question Joe.
One of my adapter projects (about half finished) is for using the C-4 behind the 51-53 331 Chrysler Hemi specifically because of the removeable bell. I also know that the C-4, with the proper pile-o-parts, will hold near 800-900hp. That is no small feat.
Why the popularity of the sbc and associated parts? I can't figure it out. Must be the kool-aid.

 

Behind a small block Ford or road going Cleveland there is no reason to convert to a TH350. The C4 will reliably do the job. And the aftermarket support is quite good for them too.

 

Nice thing about a C4 or C6 is when you start in second gear it starts off in second, rather than upshifting to second like a t-350, handy for burnouts. Good little trans that can hold big power, but won’t be cheap.

 

I’ve seen healthy big block Chevys which c4s
The reasoning I got from em was the parasitic drag was low.
Those c4s were heavily modified.

 

Agreed. My question was less about putting a TH350 behind a engine that was intended for a C4 and more about why when we do off branded swaps the default always seems to be to the GM TH350 for a basic 3 speed. But your point is well taken.

 

Less parasitic draw is another good reason I hadn't considered.

 

As I'm seeing it right now, a TCI StreetFighter C4 is actually a couple hundred bucks cheaper than the TH350 from Jeg's. I agree with you though that Ford and Chrysler parts are going to be more expensive than Chevy, but I feel like in the grand scheme of things, the difference in cost between the C4 and TH350 is negligible.

 

Because a C4 does not bolt up to any of the SBC’s in my fleet.

 

Does anyone even make a C4 adapter to a Chevy engine....or is that outright Blasphemy?!

 

I doubt that the shiverlay crowd would ever buy one so no market = no margin. Personally, I wouldn't even bother to sketch out a rudimentary design.

 

the C4 has good aftermarket support and is extremely light. Plus the added caveat of having a separate bell which makes it pretty adaptable. You can buy a bell for many applications other then Ford motors. I actually saw one with a GM bell a couple years ago.

The adapter bells are not cheap. Last I priced them they ran about 400 dollars probably way more than that today.

I think they are an excellent option for a small car. The thing that keeps me from using one is cost. I am just not in a position to drop that much cash to bolt a tranny whatever I am running. That they are a good choice if you got the cash.

 

I’ve considered using a C4 behind my 501 bbf. Still might but have to find a core C4 with a 429-460 bell. There out there but not too common and then there’s the cost of the build $$$$$…..

 

My understanding is that a lot of drag cars are using C4 these days. Cheaper, lighter, and less drag. Bells to fit a C4 to a Chevy bolt pattern are $297 on that auction site.
Chevy SBC BBC Ford SB to C4 Aluminum Bellhousing | eBay

 

Plus you get 3 gears opposed to 2 from a PG
I’m hearing they are similar in weight and parasitic drag.
Truth?

 

Got one in my car..can withstand some HP when built right..post 70 26 spline are the desirable units..I had a very well known shop do mine and it was pretty reasonable

 

Most seem to always start out in second for me after a rebuild.

 

Funny.

 

May be funny, but there's something to be said for Chevy bellhousing bolt patterns being the same for so many engines over so many decades. It makes sense to adapt something that is common, even if it's not quite the best transmission. Bonus is that if you adapt for the Chevy bell, you can also choose a PG, 200, 200-4R, 700, 4L80E, 400, 6L80E, 8 speed, 10 speed, etc.

 

Every C4 I have ever had has worked great.
Years back, I was building a Model A coupe for my Dad. The plan was to use a 322 Buick but my Dad wanted an automatic due to his advancing age. I figured that the C4 was the perfect candidate since my measurements showed that I could get it into the Model A chassis with a lot less cutting than any other automatic trans - like none. As I researched it, I arrived at the same thoughts as 57JoeFoMopar. Why isn't the C4 used more often? It's readily available, has small outside dimensions and low parasitic drag. Unfortunately, my Dad's health declined rapidly and the project went away but I still think that the C4 is underutilized.
I think a series of adapter kits for early V8s would be great. If only I was ten years younger....

 

Having a bolt on bell is a plus.

 

yeah, and now you can get bolt on bellhousings for the th350, if that's the way you want to go

 

Sure. Ya just have to cut off the old one


just easier to fix those pesky bell housing cracks.

 

yup. Ford saves you that trouble.

 

Always perfered the fords over chevy, ignore the scribble (electric water pump) and the broken case. Still worked just fine lol.

 

Growing up if we were looking at trucks to buy and it had a c4, we usually passed on em. I’ve got a SBF c6 in my save pile at home.

 

Most if not all of those sbc bellhousings are SFI approved. More of a necessity than getting tossed in the tech line. So I guess the whole trans is an aftermarket creation?

 

Looks like that bell also has the Chevy and BOP pattern.

 

^^^^^ Nope. But I did have a T350 with the pattern you mentioned.

 

JPT (Jim's Performance Transmission) in Eaton Rapids, Mi was a proponent of this, even tried to talk me into a C-4 for my Nova instead of the Reverse manual TH-400 he was building for me.
He had bells cast and everything.
Wanted me to use a full roller bearing C-4 instead. I couldn't get over how tiny it was.
I know he had a lot of guys using his C-4's in racing.
Jim Paquet, brother of Super Stock Thunderbolt racer Ray Paquet.
He's retired now though, 10 years at least.