I think the aluminum one are later year tranny's. Didn't they put aluminum OD 4 speeds in the Dart Lite and Feather Duster models in 75 & 76? I'm pretty sure this is right but someone please correct me if I'm wrong. Bill M 65 Coronet 500 'vert On Wed, May 21, 2008 at 9:34 AM, neal zimmerman <neal.zimmerman@xxxxxxxxx> wrote: > quite actually, the first couple years of the overdrive trannies were > cast iron as well. about 75 they went aluminum. Know this for a fact, > used to have a cast iron 4 speed OD > neal zimmerman, eugene oregon