A construction site reported that a Case 930M wheel loader would lose traction when climbing a steep ramp into a rock bin. The engine RPM would increase, but the machine speed would drop, a classic symptom of transmission slippage. The oil level was checked and found to be slightly low, but the problem persisted even after refilling.
The technician connected a pressure gauge to the transmission test ports. The pressure was low at the clutch packs but normal at the pump outlet. This pointed to an internal leak or a failing torque converter. The transmission was removed, and the torque converter was cut open for inspection. The impeller hub, which drives the transmission pump, had deep grooves worn into its sealing surface.
The worn hub allowed the transmission pump's drive gear to wobble, causing the pump to lose efficiency. As the load increased, the pump could not maintain the flow required to keep the torque converter filled, leading to "cavitation" and slippage. The repair involved replacing the torque converter and the transmission pump. The torque converter housing was also inspected for cracks. After reassembly and fluid refill, the loader was able to climb the ramp at full speed without losing engine RPM.
