my 2005 xterra 105k vibrates in overdrive between 40 - 60 mph, the vibration it is on and off, it fells like I'm running in a ribbed highway, when it begins I push the O/D button, it stops as soon as it slips into 4th gear. The vibration never happens except when in overdrive. I am going to change the transmission fluid and filter to see if it stops. Cannot find antone else with these symtoms...anyone?

my friend has, what he did, he brought it to the mechanics and the mechanic did the magic I didn't see how they do it but I think they replace something in it.

The vibration you feel is most likely the lock up clutch inside the convertor. Sometimes flushing the transmission fluid will help, if not its time to replace the torque convertor.