help with c6 or c4 transmission

jbolivar · Post by **jbolivar** » March 13, 2007, 4:57 pm

Hello,

I've recently purchased a 64 f100 with a 70 mustang 302. I have access to a c4 and small bell housing c6 and wonder if anyone would tell me what they think would be best. The motor has been balanced with an rv cam and it has a 9 inch rear end with 373 gears.

Thanks, Jim

ABA · Post by **ABA** » March 13, 2007, 5:29 pm

Well since you have a C6 available, I would go with it.

lincolnslick · Post by **lincolnslick** » March 13, 2007, 6:23 pm

ditto way stronger than the c4

Garbz · Post by **Garbz** » March 13, 2007, 8:01 pm

Use the C4

I will rob a lot less power from the 302. A C4 on a small block will out preform a C6 hands down.

Garbz

ABA · Post by **ABA** » March 13, 2007, 8:05 pm

What are you planning on doing with the truck?
You got a RV cam, so are you going to be pulling a boat or something else where you need a lot of bottom end torque?

Garbz · Post by **Garbz** » March 13, 2007, 8:12 pm

302 and Towing really dont mix well..........Over square bore vs stroke. Needs to rev to do anything. C6 will kill the bottom end torque the little bugger makes there fore negating any advantage.

Any reason they have bellhousings to adapt the C4 to BBF? Must be there weak....

Garbz

lincolnslick · Post by **lincolnslick** » March 13, 2007, 8:16 pm

i was talking stock trannys and i didnt say the c4 was weak i said the c6 was stronger and i would like to see how long a stock c4 would survive behind a big block

Garbz · Post by **Garbz** » March 13, 2007, 8:32 pm

A stock C4 will not bolt to a big block. With the Stock Removable bell.....

The C6 robs too much power from a 302.

In Jims other post he askd about a stang 5 speed. I sincerly doubt he wants to haul the wood anymore.

I would rater have the 300 six in place of a 302 to take advantage of the much larger torque produced in a lighter weight tow application.

Me, I love my C6, but then i have 472 cubes to waste.

Garbz

ELpolacko · Post by **ELpolacko** » March 13, 2007, 8:54 pm

Food for thought,

I just ran your engine combo through my desktop dyno program to find out where your peaks are with the typical RV cam.

RPM /HP / TQ

1000 / 40 / 212
1500 / 75 / 264
2000 / 107 / 282
2500 / 138 / 291
3000 / 171 / 300
3500 / 201 / 302
4000 / 216 / 284
4500 / 218 / 255
5000 / 204 / 215
5500 / 181 / 173
6000 / 150 / 131

Take into account the C6 will consume about 60HP at 2000 RPM, that is the meat and potatos area you need to be lugging your load from a dead stop.

Short stroke motors are fun to play with at high RPMs. Not for towing or work duty. The C4 eats less power and is plenty rugged for the task at hand.

Just put a good trans cooler on it!

FORDMANLCRACKEL · Post by **FORDMANLCRACKEL** » March 13, 2007, 9:01 pm

Lonnie

71 LONG BED · Post by **71 LONG BED** » March 14, 2007, 1:17 pm

Garbz wrote:Use the C4

I will rob a lot less power from the 302. A C4 on a small block will out preform a C6 hands down.

Garbz

Just in case you're curious, power loss for various auto transmissions:
Please remember these are approximate values, and were provided by Car Craft Magazine.

Powerglide_____18 hp
TH-350________36 hp
TH-400________44 hp
Ford_C-6______55-60 hp
Ford_C-4______28 hp
Ford_FMX______25 hp
Chrysler_A904__25 hp
Chrysler_727___45 hp

I'd go with a manual.

FORDBOYpete · Post by **FORDBOYpete** » March 14, 2007, 2:20 pm

C-6 may be stronger. But they also weigh a lot more, run hotter, and are a bear to heft up
into place w/out the right equipment besides robbing power and being slower shifting. :roll:

PLUS, I run a performance Modified C-5 which is the dual pattern Blhsg, commercial version, of a C-4. My engine
is a 460. Is that big enough of a BIG BLOCK? I turn consistent 12.60s through a 31 spline 9" 4-pinion rear gear set.
I am going on my 6th season with this street driven play toy. I have over 30K on the combo. It hasn't broken yet.
Plus, it's roughly .395 sec qwiker in a 1/4 than C-6 was with it's 22% +/-power loss coefficient & heavy extra weight. :hm:

FWIW I have friends running turbos & latahms thru built C-4s. They don't break either.

Obviously a C-4 can be broken but it's RARE if you take care of it, service it regularily,
operate within it's capabilities, and alter it to accept what you plan to do to it. I would advise using an air cooled ATF Cooler
in conjunction with radiator enclosed cooler. Use a Cooler rated for a 25K Lb RV, it will do fine. :thumright:

FBp

ELpolacko · Post by **ELpolacko** » March 14, 2007, 2:58 pm

Here is some more data to chew on.

With your gear set and a non-overdrive transmission like the C4, your RPM at 75 MPH will be 3447 with a 28" tall tire. That puts you right at the peak of your torque.

Not really realated to transmission choice but just interesting information. If you want to play around with gear ratios and tire sizes check out this website.

http://www.randysringandpinion.com/Calculators.aspx

Hawkrod · Post by **Hawkrod** » March 14, 2007, 3:44 pm

Pete and Garbz are correct, for most street trucks a C4 is a much better choice. Even racers prefer them and most classes that allow non-stock trans you will find a C4 behind a big block. there are several companies that make bellhousings for just that swap. The C4 can be built as a beast but even stock it will handle more than most 302's can throw at it. If you need a rugged beast for towing or severe street racing then a C6 is a cheaper alternative than a built C4. Hawkrod

cdherman · Post by **cdherman** » March 14, 2007, 11:59 pm

I had avery nice converstation with Jay at www.broaderpreformance.com about a year ago.

He was recomended at www.fordmuscle.com as someone that does ford trannies RIGHT.

He asserts, as do several other posters here, that a C4 can be built to handle a helluva lot of power. He also said that TOWING is what kills trannies and particularly when the oil gets hot. He recommended a tranny cooler and temp guage for the ultra cautious.

My dad has C6 in an 88 F250 that pulls 14k of trailer regularly. They have rebuilt it once already -- in 20 years. I am sure that a C4 would have died many times. But the truck is a dog mostly. A faithful dog that will go almost anywhere, but a dog nonetheless.

Unless you have lots of power to spare, or are very un-demanding, or you tow frequently and LOTS, then a decent C4 is all you need. At least that is my belief....