Hey All,
I've got what I think is a C6 auto trans in my '56. i bought it that way, so I'm not sure. Couple of questions...
How do I tell if that is what it is? C4 vrs. C6
And does anyone out there have experience in the speedo drive gears? I went to replace the speedo cable with a new one and found there is no drive gear on the old one. That's why the speedo doesn't work (as far as I know to date). My local ford dealer shows at least three dozen different drive gears with no ideas as to what goes with which tranny. I really would like to at least have some idea of how fast I'm going when the cops pull me over!

 

Hi,

Look at the case of the tranny. The C6 has the bellhousing as part of the main body, with a tail housing extension ( 2 piece ) The C4 has a separate bellhousing, case, tail housing ext. C4 has a small square pan.
You need to go to the dealer and give him the rear end ratio ( tag on rear has this) Tire size, tranny type( Auto or std.) engine size. If the parts guy is any good, he can come close. I did ford parts for 20 years and got very good at it.
It sounds like you have a later engine and tranny in the truck. If you do, tell him it is in a late 60's truck and give him the info. The rear end ratio is critical, without it , he can only guess. If the speedo is off one way or the other, you have to get a gear with +1 or-1 tooth from the first one you put in.

Barry

 

Thanks Barry,
I also got some info from the guys on the newer trucks message board. Even a picture of the pan shapes of various ford trannys. It's gonna be fun trying to get the rear end ratio. This truck came from Oklahoma and I've never seen so much baked on dirt and oil under a vehicle. I'm afraid to remove it all; it might just be holding the thing together! Lots more fun than the old English cars I've had over the last twenty five years though. Take it easy.

 

Craig,
Your data plate should have the gear ratio on it, that is assuming the rear end is original. You can get a close guess by jacking the rear end up and rotating the tire one full turn and counting how many turns the drive shaft makes, the number of turns is your ratio. The older fords usually had low gears. Good Luck.

 

I finally got under the '56 last night. Turns out to be not what I expected. There's three sections to the case, bell housing, tranny case and rear housing. Looking through the speedo drive hole there's no small diameter hole inside the case to locate the speedo drive gear. So the question is, is it worth rebuilding? It leaks pretty good right now...