Technicians A and B discuss driveshaft torsional vibration. Technician A says it can be caused by engine torque spikes. Technician B says torsional vibration is a twisting motion of the driveshaft. Who is right?

• A. Technician A only
• B. Both A and B
• C. Technician B only
• D. Neither A or B

Answer: (B)

Torsional vibration in a driveshaft is a twisting motion along the shaft caused by changes in the torque applied through the driveline. Engine torque spikes are a common source of that twisting, because sudden jumps or drops in torque excite the driveshaft’s torsional modes and create vibration. At the same time, torsional vibration is precisely that twisting motion about the driveshaft axis, not a side-to-side bend. So both statements are correct: engine torque spikes can cause torsional vibration, and torsional vibration is a twisting motion of the driveshaft.