I don't know about this, I have one of the Pontiac 2-speed auto in my 67 LeMans. As far as I am concerned it is slow & slower! This friggen car can't get out of it's own way! However, I do get 22MPG!!!!!!!!!!!!!!!!!!!! With my whopping open 2.56 rear end and turn a whole 2400rpm at 80mph! I can not wait to rip that 326 and 2-speed disaster out of the car and get my old 400/4-speed/3.55 combo back!