Drive line vibration

[pint4]

I have a driveline vibration that only happens when I accelerate slightly when travelling at highway speeds. After I ease up on the gas, it goes away. Only present when the driveline is under load at 55 to 7o mph. I replaced the front prop drive shaft-30 inches or so long. Stiil have the problem. Any ideas?
Thanks.
Bob

[old_master]

Vibration is very difficult to diagnose without driving the vehicle first hand, even for an experienced technician. With that said... what you are describing could be a worn or loose universal joint in the rear driveshaft. Or possibly the driveshaft is out of balance.