The reverse drum in the automatic transmission of Perodua Bezza, Axia, Myvi, and Alza is an essential component responsible for enabling the reverse gear operation. Found in automatic transmissions like the A4RA/A4RL (4-speed) , the reverse drum works in conjunction with the reverse clutch and hydraulic circuits to transfer torque in the reverse direction.

What is a Reverse Drum?

The reverse drum is a cylindrical part inside the transmission that houses the reverse clutch pack. It engages and holds the clutch plates when the transmission is shifted into reverse. The reverse drum operates through hydraulic pressure regulated by the transmission control system, ensuring precise engagement for smooth operation.

Functions of the Reverse Drum

1. Torque Transfer:
   • Transfers torque from the input shaft to the reverse gearset, enabling the vehicle to move backward.
2. Clutch Engagement:
   • Provides a surface for the reverse clutch pack to engage and transmit power to the reverse gear assembly.
3. Hydraulic Control:
   • Works with solenoids and hydraulic pressure to manage reverse gear engagement.

Common Issues with the Reverse Drum

Over time, the reverse drum can experience wear or damage, leading to problems with reverse gear operation. Common issues include:

1. Wear on Clutch Surface:
   • Friction from the reverse clutch pack can wear down the drum surface, reducing effectiveness.
2. Cracking or Warping:
   • High heat or sudden torque loads can cause the drum to crack or warp.
3. Hydraulic Seal Failure:
   • Worn seals can result in hydraulic pressure loss, affecting reverse engagement.
4. Contamination:
   • Metal particles or debris in the transmission fluid can damage the drum and associated components.

Symptoms of a Faulty Reverse Drum

• Difficulty in Engaging Reverse:
  • Delayed or failed engagement when shifting into reverse.
• Slipping in Reverse:
  • The vehicle may struggle to move backward, or the engine may rev without sufficient movement.
• Unusual Noises:
  • Grinding or whining noises during reverse operation.
• Transmission Warning Light:
  • The TCU may log error codes related to reverse gear or hydraulic pressure issues.
• Complete Loss of Reverse Gear:
  • The vehicle cannot move in reverse due to drum or clutch failure.

Diagnosing Reverse Drum Problems

1. Error Code Scanning:
   • Use a diagnostic scanner to check for fault codes related to reverse clutch engagement or hydraulic pressure.
2. Visual Inspection:
   • Disassemble the transmission to inspect the reverse drum for cracks, warping, or wear.
3. Hydraulic Testing:
   • Check for proper hydraulic pressure in the reverse circuit.
4. Fluid Analysis:
   • Examine transmission fluid for contamination or metal particles indicating wear.

Repair or Replacement of the Reverse Drum

If the reverse drum is damaged or worn, it may need to be replaced or resurfaced.

Tools and Parts Needed:

• Replacement reverse drum (OEM or compatible for the specific Perodua model).
• Reverse clutch pack (if worn or damaged).
• Transmission seals and gaskets.
• Perodua-recommended transmission fluid.

Replacement Procedure:

1. Prepare the Vehicle:

   • Disconnect the battery and drain the transmission fluid.
   • Safely lift the vehicle to access the transmission.

2. Remove the Transmission:

   • Detach the transmission from the engine, following the service manual for your model.

3. Disassemble the Transmission:

   • Remove the valve body and related components to access the reverse drum.

4. Inspect and Replace the Reverse Drum:

   • Check the drum for cracks, wear, or other damage.
   • Replace the drum and reverse clutch pack if necessary.

5. Reassemble the Transmission:

   • Reinstall the valve body, seals, and other components.
   • Ensure all components are torqued to the manufacturer’s specifications.

6. Refill and Test:

   • Refill the transmission with new fluid.
   • Test the reverse gear function and use a diagnostic scanner to clear fault codes and reset the TCU.

Preventive Maintenance

• Regular Transmission Fluid Changes:
  • Prevent contamination and reduce wear on internal components by replacing fluid at recommended intervals.
• Avoid Overloading:
  • Excessive torque loads can stress the reverse drum and other transmission parts.
• Monitor for Early Symptoms:
  • Address unusual noises or shifting problems promptly to avoid further damage.

If you need additional information, such as part numbers, torque specifications, or troubleshooting guides specific to your Perodua model, let me know!