Have owned our 97 astrovan awd for last 8 years 130,000 miles , developed a driveline vibration 60 mph in the last couple years and cant seem to track it down, its a high frequency vibration that buzzes inside the vehicle can feel through steering wheel dash etc. changed the front driveshaft( rebuilt) no change. changed the front diff(Used) as it was running hot appeared bearings were going in it but no change. New front shocks seemd to help but just a bit Vibration dissapears if front driveshaft removed but driveshaft appears good, noise comes and goes related to driveline load pull trailer or boat seems to go away some especially when under load Only thing i can see is some minor and i mean minor movement in the front transfer case output shaft but i jusy cannot see that being a problem. it does not make noise or vibration if up on lift and run as speed as tried to isolate that way. the vibraton tells me u joints but man, they are next to new. Any thoughts from anyone who has had and solved weird driveline problems?