what's causing vehicle to vibrate at crusing speed 55 to 80 mph ?...no vibe under 55 goes away at 80 mph.
Dependent on ambient temperature. Sometimes doesen't vibrate until 65 mph if temperature is warm (above 70 degrees.) always there after 65 mph regardless of condition,
*letting off the gas does not necessarrily effect condition, it does decrease very very little due to unloading of rear end. I think this would be natural and not a true symptom of condition...
* Inspected rear end gears ( no issue ) and changed gear oil.
* Checked rims and tires, have changed tires and re balance no change.
* Have had engine and transmission rebuilt an new mounts ..No change, Note: Engine and trans rebuilt at different times ( 6 months apart) no change in condition at any point.
Have checked drive shaft run out and replaced u joints...No change.Drive shaft yoke nice and tight.
Torque converter, flexplate, harmonic balancer all replaced. no change
Running out of thing to change / replace .Anyone expirence this vibration issue ? It is a serious vibration not some hardly noticable harmonic vibration.