7 blade fan question

Hi, Using a clutch fan saves some power and puts it to the wheels. A vibration? Are you thinking is being caused by the fan? I guess anything is possible a fan could cause this, but maybe a u joint? I had this once under acceleration only and that is what it was. Worn u joint made the driveshaft slightly out of balance. Just a thought. IM thinking the clutch fan for the car would be the fluid type (without the thermo spring on the front). I am sure others will have ideas as well... these are mine :)