Hi everyone.

Got a pair of questions for now, more to follow some other day. First, a little background...

I've got a 79 F-100 shortbed that needs an engine rebuild. I posted this a long time ago:

https://www.ford-trucks.com/dcforum/perf/937.html

What I wrote then is gonna happen this summer.

It's a 302 bolted up to a 4-speed, the one where 4th gear is like OD, not the creeper gear tranny. The tranny whines like a *****, so I want to get it rebuilt, but in the meantime I need to drive the truck, so I've gotta drop another tranny in it. I decided to go auto for the time being, as I'm not sure when I'll be able to get the 4-speed refurbed. The engine will eventually be powerful, but not crazy. I'm looking for low-end and midrange torque.

1st question, are the C-4 and C-6 interchangeable, size-wise? One is light-duty and the other is heavier duty, correct? Which is more appropriate for my intended usage? See above thread for details, please.


My 2nd question is, if all I change is the tranny, from manual to auto, will it drop in, or do I need another size driveshaft, different mounts, isolators, etc?


Shift linkage is not a concern.



Thank you in advance for whatever help y'all may provide.




Rob.

 

Changing from a std to an auto is a lot of work. You need a donor truck for parts. IMO you should just find another std tranny to drop in and sell yours for a core.

 

Forgive me, but how so?

I probably should've said this above, but if I do the swap, I'm gonna use an aftermarket floor shifter, so no shift linkage problems worth getting all worked up about.

Vaccuum issues? Shouldn't be a problem.


Kickdown linkage and accessories?

Now, that one will take some parts scrounging, I admit. But other than that, what else would be ought to scare me off?


Rob.

 

The C4 bell housing bolt pattern is for the windsor family engines, so it will be the easiest to find in junk yards. There are C6 transmissions with the same bellhousing but they are more difficult to find in junk yards. You will need to get a driveshaft from a C4 equipped truck, yours wont fit. You should be able to get the kick down rod off of the same truck.

There are 2 types of C4 transmissions, case fill and pan fill. I know most if not all C4's in trucks were pan fill, I am not sure if a case fill will fit. I have also seen pan fill C4's in bigger Ford cars of the same era, LTD's, ect.

I don't know about the crossmember, if you will have to move it or not. but i am pretty sure you will need a new transmission mount.

One thing to remember, if there is no visible damage to the truck, something got it to the junkyard. Junking an old truck because the transmission went bad, is something alot of reasonable people do. Around here they drain most of the fluid and it is really hard to tell the quality of the transmission with out fluid to look at. The one I have now is from the local boneyard and it slipps badly. I am running it until I can get an AOD and swap rear ends.

Having a parts truck would be a big help, if for nothing else, to cut down on the time neeed to make the swap complete. Who wants to get 90% of the way through the job to find out you need a clip to hold the kickdown lever on. Not like I would know anything about that.

hope that helps

 

Check out some of the other posts in this forum on the same subject.