Initially felt like a bad ball joint - like the wheel was bouncing around at 60-65mph. However, as soon as there was neutral or negative load on the drive train the vibration ceased entirely. Over 70mph the vibration became somewhat dampened.
The vibration has now become worse over the last several days and feels this way at all times above 20mph through acceleration. The car coasts perfectly with neutral load. However, has started vibrating with the negative load of deceleration.
This is not a wheel bearing. This is not a suspension issue(checked all linkage, alignment, tire balance). I have checked the motor and transmission mounts and they seem fine.
The frequency of the vibration bears no relationship to tire rotation or engine RPM. I've run it through all gears. Shifting is smooth. Frequency seems very constant without regard to speed or rpm.
This is felt through the vehicle chassis, not the steering wheel. Feels possibly stronger in passenger seat than driver's but only by a small percentage. Seems to come from center to center-right of engine compartment.
The vibration is no longer subtle. If this vibration were due to a bad ball joint, it would be a very bad, dangerous situation.
Car shows no diagnostic codes.
Suspect transmission, perhaps a shaft bearing.