Hi,
1989 Aerostar, 3.0LI get a rumble sound on the highway, but with no additional vibration. it is coming from the rear of the Van, near the muffler area, but that is close enough also to the rear end. I just want to rule out that it couldn't be the rear axle, or the differental that is making this sound... I have replaced the muffler 2 years ago, and there is just a touch of surface rust, but nothing bad (no rust through) I know that internal baffles can go bad - again, I can live with the noise until I can change the exhaust (from the converter on back), But I just want to be sure I'm not in danger on the highway.