C4/C6 Comparo

Can anyone help explain the differences between a C4 and a C6.... I am going to replace my tranny this summer and was wondering if I should stick with the C6 or go with a C4.

The difference between a C4 and a C6 is that the C6 uses larger parts that the C4 and it uses a reverse/low clutch instead of a band. The difference in strength when properly built is about 500 HP at the top end. The C4 (properly built can handle 1000+ HP and the C6 can handle 1500+ HP. The C6 needs a steel rib on the pan area because it is so big to take more that about 800 HP. Otherwise there is a danger of the case twisting to the point of fracture. We used a 1x2" steel transmission "spacer" to stiffen the case and provide a deeper oil reservoir. It is mounted to the case with a sealer and no gaskets and held in place with double ended studs with a hex head counter sunk into the spacer.

A little more on your application or what you are going to do with your vehicle needs to be known .
C6's are tough . So are C4 but require more expense for parts to live with power. A basic C6 with few mods,transgo kit and #9 roller thrust wil give you earsof service.

All I have is a 72 torino with a mild 302. My future plans are just to make this a cruiser. I've been driving a C6 with no 3rd gear for the past year and a half, and therefore, constantly spinning more than 3000 rpms for extended periods of time (highways), and yet the thing hasn't died yet. But say I wanted to change to a C4, what modifications would I need?

C6 for is a good and very strong trans. They take far to much horsepower to run them. C6 are great for Monster Trucks. My feeling is a well built C4 is good for about 800 HP, some say 1000 HP. Once you get over 600 HP the life the the C4 shortens quickly. I think once you get way up in horsepower, your better off with a power glide. Chevy guys always use ford nine inch for strength, we might as well use a power glide, they do hold up and are reasonable to buy. Hey there's guy's running C6 transmissions, but at the price of performance.

John

Originally Posted by kokkas

C6 for is a good and very strong trans. They take far to much horsepower to run them. C6 are great for Monster Trucks. My feeling is a well built C4 is good for about 800 HP, some say 1000 HP. Once you get over 600 HP the life the the C4 shortens quickly. I think once you get way up in horsepower, your better off with a power glide. Chevy guys always use ford nine inch for strength, we might as well use a power glide, they do hold up and are reasonable to buy. Hey there's guy's running C6 transmissions, but at the price of performance.

John

I agree...i have heard the C6 may suck as much as 50HP vs C4 @ 20HP or so. If this is not tow vehicle or race car - a C4 should work fine.

To swap to C4 you'll need flexplate, converter and trans and different driveshaft and rear mount will likely need change too. Shift linkage also will be different unless you have a aftermarket cable shifter..
For the cost of the conversion though if just a street car/ cruiser you prob won't feel any big gains .

Hey I recently purchased a C4 from Redneck trans, and they sent me everything but the shifter for the swap. There transmissions are second to none, ours works amazing. And one more thing the price is right, I had to share this with everyone.
Very nice to deal with. Also trans mission good for 800 HP so good for most of us.

John