C4 vs C6

[akforsyth]

So in my travels I have been looking for a c4 transmission for my sons bronco and came across a guy who wants to ditch a c6 transmission from a SBF for the same price as C4's are going for around here. Now other than the obvious differences mentioned in John's tech article on the C6 is there any other reasons the a C6 may be better/worse than a C4 for a bronco. It will have a mildly built 351W in front of it and probably spend most of it's time off road with a little bit of inroad transiting. Cheers

 

[omureebe]

The C6 is heavier and takes way more fluid. I put one behind a 351 (Merc Cougar) and regretted it from a total weight perspective. I'll upgrade my Bronco this winter with a mild 351 and will keep the C4. Also..... the bell housing on Bronco C4 is different than a passenger car C4 or passenger car C6. Someone will have to chime in on what the difference is... Why not just go with a Bronco C4 and upgrade clutches?
Omar

 

[akforsyth]

Why not just go with a Bronco C4 and upgrade clutches?
Omar

That has been my plan originally. This C6 just popped up close by and is the right bell housing pattern. My original thought was to overhaul a C4’s and upgrade it while in there. What’s the worst that could happen right?

 

[Bronco4x4]

I don’t know the exact numbers but was told that the C6 will also steal more Hp than the C4 to operate.

 

[Broncobowsher]

The C6 is a stout, heavy, large transmission.
Length is the biggest hurdle in a bronco, that rear driveshaft can only be so short. And the shorter it is the worse the angles get.
Height is another issue. If I remember correctly the truck C6 has extra ribs on the top of the transmission for structure, those get into the tunnel.
They are well known for taking a lot of power and surviving, but they also take a lot of power to operate. I remember hearing once up to 40 HP loss from the drag in the transmission.

Heavy early 70's big block luxo barge, big block truck, motorhome. Good uses of a C6. Also found in some airport tugs and other industrial applications. But not a good pick for a Bronco.

 

[ugly74]

^^^What these guys said^^^
The C6 is a beast and can take a lot of abuse. But it is big, heavy, and there’s more parasitic power loss with it, vs a C4.

 

[Rustytruck]

there is also the transfer case issue too the dana 20 doesnt bolt up to the C-6. so its adapters or a 205 with shitty low range and more added length.

 

[brewchief]

C-6 does have its downsides and is not going to be a bolt in deal, however if you are someone like me who couldn't keep a C-4 alive then it's a decent option. I've got one going in my bronco in the next few weeks, I will be using the 205 transfer case as well since a higher low range will benefit me.

If you are just building a cruiser then one of the overdrive autos might also be an option, they also seem to have more support as far as ready to bolt in options, the C-6 has little support like that.

Sent from my SM-G965U using Tapatalk

 

[bronconut73]

I read quite a few years ago that the C6 robs the most power of all of the auto trannys and ironically the C4 robs the least power of all of the (stock) auto trannys.
You can build a lot of parasitic losses out of any tranny, but the C4 does really good at that in stock form.
Modified C4's are still a hot ticket in the drag racing world. It can be built to take ridiculous power.

 

[sprdv1]

That has been my plan originally. This C6 just popped up close by and is the right bell housing pattern. My original thought was to overhaul a C4’s and upgrade it while in there. What’s the worst that could happen right?

Inquire locally or on here for someone nearby that could potentially help rebuild your C4?

 

[sprdv1]

Been made to work, but not an option most go with for sure

The C6 is a stout, heavy, large transmission.
Length is the biggest hurdle in a bronco, that rear driveshaft can only be so short. And the shorter it is the worse the angles get.
Height is another issue. If I remember correctly the truck C6 has extra ribs on the top of the transmission for structure, those get into the tunnel.
They are well known for taking a lot of power and surviving, but they also take a lot of power to operate. I remember hearing once up to 40 HP loss from the drag in the transmission.

Heavy early 70's big block luxo barge, big block truck, motorhome. Good uses of a C6. Also found in some airport tugs and other industrial applications. But not a good pick for a Bronco.

 

[akforsyth]

Thanks everyone. I am going to stick with my plan of rebuilding a C4.

 

[Bronco4x4]

You can request the rebuild kit to be for a higher Hp engine. The clutch packs are designed for a perfofmance engine.

 

[sanndmann3]

C4 is a neat little trans that can be built to handle some serious hp. Pretty simple to rebuild too. I don't see any advantage to the C6.