Transmission input wanted (C4 vs C6)

[Jim Oaks]

Hey all,

TRS-1 is going to be starting a solid axle rebuild this spring.

One concern I'm having is a lack of power for the heavier axles, wheels and tires. I can regear to compensate for tire diameter, but I still have an issue of added weight.

I have a healthy 302 V8 that I'm going to keep for now, but later down the road I may decide to switch to a 351W block.

This brings me to the transmission......

I'm not sure if I should keep the C4 or swap up to a C6.

I know the C6 is considered a heavy duty transmission. I'm wondering if I should upgrade to the C6 since I'll be turning more weight and possibly adding a 351w later. My reason for deciding this now is so I don't have to make driveshaft changes later. I'd rather have everything setup and just change from a 302 to a 351W later.

Is a C6 worth it? Is the C4 sufficient? I'm not going to build a high horsepower drag motor for this truck.

I had read on another ford truck site that the C4 "Eats about 60 less HP than a C6."

In another year I plan on helping Vanessa start her own truck. If I upgrade now, I can keep the C4 I have now with the A/A adapter and stick it in her Ranger.

 

[baddis]

i would think that if you are staying close to stock hp the c4 should be fine. doesn't the c6 have a larger bell housing and converter?

 

[Mutant Pony]

PA has a c4 rated at like 1500hp. The c6 can easily be modified to not use much power. There are a lot of performance parts out there for either trans, a few more for the c6. The c6 can be geared lower. (1st and 2nd).

 

[Lifted2x]

I have seen c-6's put through a lot of punishment. They are known for running cool and chances are once its in there you wont have to mess with it ever again. I remember my dads old work van had a 302 and c6 that he used to pull a 24 travel trailer completely packed full of stuff from LA to Oregon. Only went about 15 or 20 up the pass but never had a problem with it.

 

[Gotta_gofast]

I think a little work done to your C-4 trans will be sufficient. I've seen some healthy small blocks abusing C-4s and they take it well. But, like mutantpony stated, you can get a "wide ratio" planetary for a C-6.

 

[mongo]

i actouly just looked for myself the c4 is better fow power and they make reverse valves for them so you can bump shitf with out over shooting into reverse ... the c6 is much much heavier duty there hevier and take a little more rpm to get going


c4 for a street or extream hp woods truck but c4 for anything else

 

[1wicked88]

Having used and built both of them, for what you are doing with the truck a C4 would be fine. Yes you can build a C4 strong but if you think you are going to make too much power for it, why polish a turd and throw lots of money at it? Not that C4 is bad, its isn't by any means I love that transmission. The C6 is a bit larger and takes a little more power to use but if that is a concern you can use the above listed planetaries as well as a torrington bearing kit and it will be quite efficient. I personally have exploded a C4 as is splitting the case from over powering it. You aren't going to see 1000hp on many stock C4 cases, most are aftermarket and use a blow proof bell reguardless. Even with a C6 for over 600hp I would cut the bell and use a blowproof. Each has it's pros and cons. If you keep it under 400hp I'd stay with a C4, it will work and you won't have a million bucks in high end parts but more power than that I would start with a C6.

Matt