Hiya
I just bought a 1995 Ford E250 Cargo van with 3-speed auto, 4.9L L6, 176k miles. The tires are brand new Kumho Road Venture AT (P225 75R16 104S) truck tires. The car drives fine at normal speeds but I do hear some knocking/wobbling sounds coming from the passenger side front wheelwell that goes away while the brakes are applied. The major problem is that when driving at highway speeds from 55-70mph a loud deep vibration/resonance is felt throughout the cockpit.. it feels and sounds like I'm sitting on a huge vibrator for lack of a better description. There is also a quiet high-pitch whining sound that increases along with the deeper rumbling/vibration. It seems like the entire vehicle just starts resonating at this speed and it increases as I accelerate from 55 to 65mph. Above 70mph the problem seems to taper off. I've tried opening the windows with no effect. Also just had to put in a new radiator and fan clutch for cooling reasons which didn't alter this problem at all. This is going to be a major problem for me because I'm about to do 1500 miles highway driving cross country not only for comfort but I worry about gas mileage being affected as well. Already had the alignment and tire balance checked and corrected without fixing the problem. The mechanic has also checked everything over underneath the car and could find nothing loose or seemingly wrong that could cause the rough highway driving. Is it possible these Kumho 'AT' tires are to blame for the problem or should I check other things? I don't do any off road driving and I'm wondering If I should have forced them to install some less aggressive tires.
Any help is appreciated as always
thanks Jay