C6 differences

Sharkdance · Post by **Sharkdance** » Sat Mar 11, 2006 10:12 am

I have two C6 transmissions.

1) C6 out of my 70 F250 with a cast iron tail section and a speedo cable hook up on the right side.
This one leaks everywhere and shudders when hot in reverse but otherwise runs great.

2) C6 out of my 72 F100 donor truck with a alloy tail section and a speedo cable hook up on the left.
Unknown condition but was full of clean fluid when pulled.

Any advice which one is better to use? Is the cast iron one better/stronger?
My plan is to put my truck back together with one or the other and rebuild the spare one in time while still driving my truck.

See photos for tail section differences:

pat67shorty · Post by **pat67shorty** » Mon Mar 13, 2006 2:30 pm

The only real difference between the two si the iron vs aluminum tail. The iton one is stronger... but you won't break a tail unless the trans mount completely breaks.

So, use the fresh tranny. The difference is neglegable.

390Nut · Post by **390Nut** » Mon Mar 13, 2006 2:41 pm

I've been told the difference is in longevity; if you use the vehicle for towing/hauling alot, then the iron shaft with the flat, bolt-up yoke is more durable in the long run.

Just second hand info though, no personal experience here as I've always owned/driven sticks.

Sharkdance · Post by **Sharkdance** » Mon Mar 13, 2006 10:33 pm

Thanks for the info guys. You confirmed what I was thinking.
But the condition of the donor tranny is unknown. Im leaning twards re-sealing my old one and run with it for a while.
I might try to sell the donor C6, or use it as a guinea pig to learn on.

fordman · Post by **fordman** » Mon Mar 13, 2006 11:30 pm

that is something i didn't know you said the speedo hookup was one different sides of the two trannies. mine is on the drivers side and its a 68. i guess they changed sides for a reason. maybe it is heavy duty or something.

71-F-250SC-72-F-250C · Tue Mar 14, 2006 4:40 pm

Mines on the drivers side also and it is a 72 the 71s is also on the drivers side.

CJ,s 67 F100 · Post by **CJ,s 67 F100** » Tue Mar 14, 2006 5:32 pm

Mine is on the passenger side, you know your tranny has a problem and you dont know about the donor truck tranny but it does have clean fluid in it. Personally I hate to pull a C6 so I'd ether install the donor that might be ok (you know yours isnt)or I,d take both trannys to a tranny shop and let them make one out of the two to keep the bill down. Just my 2cents. Good luck Charles

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