C4 in an F250

[fomocoguy]

This is really an information search and a hypothetical question. Since I know we've got some trans experts here I'd like to hear what you all have to say!

So, one day when I finish my 300 build I may be inclined to put an auto behind it. I drive my truck to relax and have fun and sometimes I'd rather not have to shift, plain and simple. I happen to have a core C4 sitting here doing nothing that would bolt to my 300 just fine. I hear all the time that a C6 robs a noticeable amount of power and that a C4 is better in that way.

SOOO, the big question is if some companies build C4's that will hold up to 600 hp race cars, can a C4 be modified to hold up to a 5500 lb 4x4 with a 250hp 6 cyl? What's the weak link, if any, and can it be fixed?

[PhantomoftheBumpside]

You are going to have to make sure you have the proper output shaft...

Other than that would recommend...

A good shift kit
Direct clutch power pack
Red Eagle Clutches + Kolene Steels
6 pinion planetary

Remember you are going to be trying to turn twice as many tires that are bigger than the usual two... the more slip you've got, the more heat you've got and the more heat you've got the quicker the tranny in your toy is gonna break.

[fomocoguy]

By proper output shaft, are you referring to the bigger one from the later C4's or do you mean one that will work with my divorced t-case?

I still would like to know why you don't see them used on bigger trucks. Is everybody just inclined to use the C6 because a stock build is more than tough enough to handle towing and hard work? I suppose so.

What about the power loss through them? How does a C4 compare to a C6 in that department?

[PhantomoftheBumpside]

Yes, you'll have to make sure you can mate with your T-case.

Yes, C6's are built for the application, C4's not so much. Thinking about it, you should probably get a upgraded band as well... if you were upgrading a C6 you'd also have options for OVERSIZE and Kevlar bands. (C6 wins)

Loss is slip (slip is heat, heat is damage...) - How much or how little you will have depends on the parts, the build and the age (wear). Percentage wise C6 has larger surfaces so will have less wear in properly built and maintained trans given the same loads and duty cycle... (C6 wins again)

[Donnie]

Hi, 90 % of heat generated in an automatic trans is coming from the converter, not slipping clutches, or the band/bands whatever you have. That is why the fluid leaves the converter & heads for the cooler..The higher the stall in the converter=fluid shear, or heat inducing capacity.
The only clutch that can create a lot of heat is the converter clutch, which you are not to be concerned with in the C4 - C6.......I have seen a LOT of purple converters in the later model lockups.E4OD's---4R100's-----all GM's since the E cubed, or constant variable slip was introduced.
I'm getting off track, back to base........The weakest link in the stock C4 is the 3 pinion planet. Same for the Stock C6...spline strip out...& yes you can build a C4 to take a lot of punishment, but the heat treated, 6 pinioned, large servos, bla, bla , bla...all cost bigger bux.....Donnie