I have a 1975 model with a 2.3 liter automatic. At speeds over 60 MPH I'm experiencing a noise similar to this: vrump...vrump...vrump along with steady vibration. It sounds like engine but feels more like tranny. I know the tranny was swapped at one time. Is it possible that the drive shaft angle is not correct? Or, maybe this is normal noise for a four-banger at higher speeds?