A manufacturing plant reported that a TCM FD30 diesel forklift would not move in reverse. Forward travel worked fine. The transmission oil level was correct.
The technician jacked up the rear of the forklift. In a TCM transmission, "Forward" and "Reverse" are controlled by separate clutch packs. He removed the "Control Valve Cover" on the transmission housing. He applied 12V power directly to the "Reverse Solenoid." The solenoid clicked, but the wheels didn't turn.
He then removed the "Transmission Oil Pan." He found a large amount of black friction material (clutch dust) in the bottom. This indicated that the "Reverse Clutch Pack" had burnt out. He removed the transmission and disassembled it. The "Reverse Friction Discs" were charred and worn down to the metal plates. The "Separating Springs" (which release the clutch) had lost their tension, causing the clutch plates to drag even when not engaged, generating heat.
The burnt clutch caused the debris that clogged the "Shift Control Valve." The debris prevented the "Reverse Spool" from moving fully, limiting the oil flow to the clutch.
The repair involved replacing the reverse clutch pack (friction discs and steel plates) and the separating springs. The control valve body was ultrasonically cleaned to remove the debris. A new transmission filter was installed. After reassembly, the forklift moved in reverse smoothly. The technician advised the operator to stop "power-shifting" (changing direction without stopping), which caused the clutch overheating.
