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C4 or C6?

7K views 18 replies 8 participants last post by  gregaust 
#1 ·
I'm making the mental list of drivetrain parts for the '32 and have come to the trans. I really like how the big bell/short tail C4 worked out in the '31 but that is behind a stock 5.0 HO. The C4 weighs less and I know what parts I'll need to mate one to the 545, but the question arises.... which can be built reasonably to handle 6-700 hp in a light street car? Can a C4 be built/modified to handle reasonable HP and torque or am I better going C6?
Pros and cons of each?
 
#3 ·
Sounds like a C6 is the way to go. I've been reading about some of the mods... extra clutches, oiling mods, etc. Apparently, the C6 is about 30-35 lbs heavier so the weight isn't that big of a deal, and the longer tailshaft won't be a problem with a triangulated 4 bar. I'm guessing this car will come in around 2500 lbs and will need about 4" of setback.
The engine going in it is a D9 block 12.5:1 forged internals with SCJ-B heads, Torker II and QF 950 DP. Guess I'll have to run the Sanderson shorties unless someone knows another vendor making shorties or block huggers for CJ ports. Scotty'll have to grind another cam, too.
 
#6 ·
Yes, I will.....hehe.
Doing a little more research I've found Ford made a short tail C6 used in 70's F250's but reliable info beyond that is hard to come by. 4X4's with a divorced xfer case had the short tail but I'm looking for that trans with the BB bellhousing (would have been 351m/400) not FE. It sure would help with drive angle on this short of a wheel base and having to set the engine back about 4".
 
#11 ·
Slowride,I believe the short tail truck c-6 you are referring to is the one used in a lot of late 60's early 70's FE powered 2 wheel drive pickups.It had a short cast iron tailhousing but used a bolt on yoke instead of a slipyoke,and in longbox trucks was typically used with a 2 piece driveshaft(not sure about shortboxes).By the time ford started putting 460's in the mid 70's trucks they had reverted back to the long tail trans with a slipyoke all the ones I've seen were for FE never seen a 460 version,but if your building a trans there's no reason why you can't use those parts from a FE core,you'll just need 2 cores trannies to build 1.Also the tailshaft is coarse spline.This trans was also used in FE powered 4x4's with divorced t-case,but since Ford never offered 460's in 4x4's in the 70's you won't find 1 unless you stumble across 1 someone built for a swap.
 
#15 ·
Found one but not locally and it'll be trucked in. Now on to modifications. Automatics are not my deal so have been doing a little reading up. I've read of oiling and roller bearing mods for a C6 that are recommended for higher horsepower applications. I'm not talking about big HP here (7-800), so anyone have feedback on what the trans will require for these power levels, street/strip use in a relatively light car? I'll also have to start thinking stall and gearing to use with a 30" tall tire as well.
 
#17 · (Edited)
here are 2 easy ways to tell between a C4 & C6. A C4 has 11 bolts in the pan, a C6 has 17 bolts. A C4 has a bolt on bellhousing whereas the C6 case is all one piece.

There are 2 models of C6: Big Block and Small Block. The bellhousing bolt patterns are different.

The C6 is a very tough gearbox, you'll never break one with a street 351, but they do chew up more power than any other 3 speed.

The C4 is also quite a tough little gearbox and doesn't eat up much power. In a high performance application, they are easily modified to cope.

For a street engine, I'd go for the C4

All the best: simple crm for small business
 
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