Then by process of elimination its from the drive train assembly that is rotating. Transmission, axles, brake rotors, wheels, or tires. We dont need to keep going round and round do we?
yes any part of the drive train that rotates can cause a vibration if damaged or imbalanced. However I would expect it to vibrate all the time, not just when under load. Inspect it anyways though.
are you on adjustable height suspension, raise the car to stock height if you do. if the vibration stops, sorry bud. its youre axles. been thru many a set to figure out thats what it was.