A logistics warehouse reported that a Linde E20 electric forklift vibrated violently when driving straight, especially at high speed. The vibration stopped when turning. The steering also felt loose.
The technician tested the drive motor. In Linde forklifts, the drive motor is mounted vertically on the rear axle. He disassembled the motor. On the motor shaft, there is a "Rotor Position Encoder" (a magnetic ring) that tells the controller the motor's position. He found the magnetic ring was cracked. The crack caused the sensor to output an erratic signal. The controller reacted to this by constantly adjusting the voltage, causing the motor to "cog" or vibrate.
The "loose steering" was a separate issue. He jacked up the rear of the truck. The rear axle pivot pin (the large central bolt that allows the axle to oscillate) was worn. The bearing race had pits (brinelling). This allowed the entire chassis to shake horizontally on the axle, amplifying the motor vibration.
The repair involved replacing the motor encoder ring (using a specialized installation tool to ensure it was seated flush). He also replaced the rear axle pivot bearing and adjusted the lock nut torque. After reprogramming the controller to recognize the new encoder, the truck accelerated smoothly without vibration, and the steering felt tight and stable.
