Transmission Swap Blues


Davey’s had a long haul returning to roadworthiness…and now apparently we’ve got one more hurdle to cross (and I’m hoping that’s it!) After the original engine swap from a 144 cubic-inch inline-6 to a 200 c.i. inline-6, in which we mated it to the original manual transmission, we changed out the transmission for the C4 which had come with the 200. After finally getting the Ford Falcon on the road a few weeks ago, it came to our attention that the C4 transmission didn’t want to shift into third gear. Since you can pick up a C4 on Craigslist cheaper than you can rebuild one, that’s what we did. Today we set out to change the Falcon’s transmission once again. They say “third time’s a charm,” right?


As it turns out, a C4 isn’t simply a C4. A transmission used widely in Fords from the 60s into the 80s, C4s are extremely common. If you ever need to replace one, it will be helpful knowing that there are some differences to keep in mind. First there’s a dipstick placement difference, then there’s the bell housing which will be different for V8, V6, and I6, and finally there’s the input shaft splines. (If all of this vocabulary confuses you…I completely understand! I’ve made you a handy diagram at the end.)

We didn’t have need to investigate our splines when putting the trans in, so not until dropping it today (after purchasing a new C4 on Craigslist for $200) were we sure what we were dealing with. As it turns out, the C4 we took out of the Falcon has an input shaft with 24 splines going into the trans and 26 splines going forward into the torque converter. The C4 we got from Craigslist has 24 splines on either side and has a torque converter from a V8. In order for it work on the Falcon we need to put the torque converter from the transmission we just pulled out and put it on the one we’re putting in…but because of the spline difference it doesn’t fit. Now we’ve got to find a torque converter for an inline 6 that fits 24 splines.

Ahhhh…garage set-backs…that’s part of the hot-rodding life! The more you do this though, the more knowledge you have to guide you along the way.


For you beginners out there here’s two additional helpful hints:

1. When working underneath a car, put on a pair of safety glasses. I always try to start out without them because they’re so darn ugly (unless you get a super cool vintage pair like my buddy Lori). But then debris falls from the underside of the car into your eye – or worse, a bolt or heavier object flies for your face – and you’ll be wishing you had them on. Save yourself the trouble and just wear them from the start!

2. One of the most overwhelming things for me when I started wrenching on cars was vocabulary, I would try to read articles and such but so easily got confused as I didn’t know the terminology. Here at GreaseGirl, I’ve been meaning to do a better job at defining some of the terms we throw around in the garage…and I’m personally still working on graduating from using words like “that thingy”, “whatsit”, or “thingamabob” when trying to describe something! So here’s a quick diagram of the parts I’ve just referenced above…


I hope my next Ford Falcon update will be about how great Davey is to drive! Until then…

Happy Trails,

5 Responses

  1. jpkalishek

    I now wear my safety glasses nearly constantly while working on my bikes, or under/on my truck …. I got the bifocals from Walmart because my arms stopped being long enough to read. Yeah, Old Folks Eyes hit me at 42-43 and I can’t work close without them any longer.

    • jpkalishek

      Doesn’t your 24/26 shaft fit into the new tranny? I never messed with too many autos … I’d likely be going the other way, and did in my old ’73 Colt when I yanked the Baby 909 and stuck in a 5 speed from a Conquest

      • greasegirl

        Good thinking JP…but the 24/26 is slightly larger in diameter…whanh, whanh, wha. I ordered a torque converter today, fingers crossed that it works!

      • jpkalishek

        Ah the joys of mechaninckle work. One of the reasons I swaped the tranny in my Colt was the starter went out. My engine was a 2.0 and for the first ones, the starter was different than anything else. I had it rebuilt and they messed up, it ran backwards. He rewired it, but the things still had an issue so he gave me a brand new one from Dodge or Mitsubishi but it was for all the other years and models. I prefer standards anyhow, had almost everything I needed anyhow. Then once I got it all together I learned I only needed to shave the starter opening a bit and the regular starter will line up.
        Later the water pump needed changing. Yeah, again it was only available two years so no one had one new, reman, or used. I ended up getting one for a later year, pressing out the bearing and seal then very very very carefully pressing out the old one from my housing and stuffing the new one in there. Yep, I rebuilt my own…
        I then stuffed my old one back into the new and returned it for the core charge.
        Later, again, I learned I likely could have gotten a new one from the Mitsubishi Fork Lift dealer. Apparently they kept using that engine there for many years after the road version changed to the balance shaft design.

  2. Lori

    Wow! I totally would have thought a C4 was C4. Who knew?? Good luck to you my friend!! Davey and Bondorella need to cruise together soon!


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