Which C4 works?

Discussion in '1974 - 1978 Mustang II Talk & Tech' started by 77CobraResto, Feb 13, 2004.

  1. This is really a great forum. I have lots of questions on my 77 Cobra II but I'll start with this one. I have two C4 trannys and access to an AOD. None are original Mustang II. One C4 is a '68, the other is around an '81 and the AOD is from an '86 truck with a roller 302. I want to use the Mustang II bellhousing, torque converter and flywheel so the few remaining hedman headers out there can be used as well. Mustang II's came with C3 and C4 trannys. I'm not sure if the input shafts from my transmissions will work with a Mustang II torque converter. From what I understand, the input shafts from Mustang II transmissions are smaller. Any help with this will be greatly appreciated.
  2. Either one of those C4's will work for you. The C4 in the II's use the standard 26 spline input shaft which is the same for any C4 1964 and up. There was however, some C4's from '66-'69 that used a 24 spline input shaft. The other difference in this '66-69 C4 is the valvebody. The AOD won't do you any good. You cannot exchange the bellhousings and in reality, it's a real tight fit in the II and should only be considered if you must have that overdrive. Headers are not an option at all with the AOD. And if I recall, the truck AOD isn't a slip-yoke tranny anyways, unless it was in a shortbox p.u.
    Your best bet is to use the '79 tranny and if you don;t have the MII bell, tq converter, and flexplate, just use the '68 C4 bell you have and it will work with your '79 C4's converter (as long as the converter's bolt circle is 10.5") and all that will fit into the II. The headmans can be massaged just enough to work with the non-mustang II bellhousing. The Dynomax/Blackjacks will not fit at all with the full size bell. The reason for using the '68 bell is simple, look at the back slope of the '68 bell and look at the '79 bell. You'll notice the '79 is more rounded and sticks out a bit wheras the '68 bell drops off quicker and provides much more firewall clearance. Fox body guys really like the earlier bells (like your '68) aswell.

    There is no difference between input shafts on ANY of the C4's other than what I mentioned above. There is a difference between a few C4's used specifically in the Mustang Ii's though, Some were fitted with a beefier pinto trans thus having a totally different valvebody and 1 less clutchpack than your std. C4 tranny. Try to steer clear of these anchors. Good for V6's and I-4's but a short life span behind a V8.

    Hope this helps! :nice: