Mercedes-Benz vehicles are renowned for their engineering excellence and luxurious driving experience. To ensure your Mercedes continues to deliver peak performance, regular maintenance, especially of vital components like the transmission system, is crucial. One of the most important aspects of transmission maintenance is changing the transmission fluid. While it might sound daunting, changing the transmission fluid on your Mercedes, particularly models with the 722.6 transmission, is a task that many DIY enthusiasts can confidently undertake. This guide will walk you through the process of a Mercedes Transmission Fluid change, focusing on the 722.6 transmission, ensuring your vehicle’s longevity and smooth operation.
Understanding Your Mercedes 722.6 Transmission and Fluid
The Mercedes 722.6 transmission is an electronically controlled 5-speed automatic transmission that was used in a wide range of Mercedes-Benz models from the mid-1990s to the mid-2000s. This robust transmission is known for its durability, but like any mechanical system, it requires regular maintenance to perform optimally. Mercedes transmission fluid is specifically formulated to lubricate, cool, and protect the intricate components within the transmission. Over time, this fluid degrades due to heat, friction, and contamination from wear particles. Old or degraded transmission fluid can lead to a host of problems, including:
- Rough Shifting: Gears may shift harshly or hesitantly.
- Transmission Slippage: The transmission may slip out of gear or fail to engage properly.
- Overheating: Dirty fluid reduces cooling efficiency, leading to overheating and potential damage.
- Premature Wear: Inadequate lubrication accelerates wear and tear on internal components.
- Transmission Failure: In severe cases, neglected transmission fluid can contribute to complete transmission failure, a costly repair.
Regular Mercedes transmission fluid changes are therefore essential preventative maintenance. Mercedes-Benz recommends specific intervals for transmission fluid changes, which can vary depending on the model and driving conditions. Consulting your owner’s manual is always the best first step. However, as a general guideline, changing your Mercedes transmission fluid every 40,000 to 60,000 miles or every 4 years is a good practice to maintain optimal transmission health.
DIY Mercedes 722.6 Transmission Fluid and Filter Change: Step-by-Step Guide
Before you begin, it’s important to gather all the necessary tools and materials. Working in a well-lit and safe environment is also crucial.
Tools and Materials You’ll Need:
- Jack stands (4)
- Floor jack
- Torx socket #30
- 5mm hex socket
- Socket wrench with extensions
- Torque wrench (inch pounds and foot pounds)
- 27 mm socket
- Long breaker bar (for crankshaft pulley nut if needed)
- Mercedes transmission dipstick tool (essential for accurate fluid level check)
- New Mercedes transmission filter
- Infrared thermometer (for checking transmission fluid temperature)
- Long neck funnel (designed for transmission fill tube)
- Rags or shop towels
- 7-9 liters of Mercedes-Benz approved transmission fluid (check your vehicle’s specification)
- Drain pan
- Cardboard or newspaper to protect the floor
Procedure:
1. Vehicle Preparation:
- Safely lift your Mercedes using a floor jack and securely support it on four jack stands. Ensure the vehicle is level for accurate fluid draining and filling. Using plywood between the jack stands and the car’s frame can provide added protection.
- Place newspaper or cardboard underneath the vehicle to catch any spilled transmission fluid.
2. Draining the Transmission Pan:
- Locate the transmission pan drain plug (it’s usually quite obvious) and use a 5mm hex socket to remove it.
- Allow the old transmission fluid to drain completely into the drain pan. You should expect to drain approximately 3 liters of fluid from the pan.
- Once the fluid has drained from the pan, use a #30 Torx socket to remove the six bolts securing the transmission pan. Be prepared for some residual fluid to spill as you remove the pan.
3. Inspecting and Cleaning the Transmission Pan:
- Carefully remove the transmission pan. Observe the color and smell of the drained fluid. Dark, burnt-smelling fluid or the presence of metal particles in the pan can indicate potential transmission issues.
- Clean the transmission pan thoroughly using a lint-free cloth to remove any sediment or debris.
4. Replacing the Transmission Filter:
- Locate the transmission filter. It is typically pressed into place and doesn’t have any bolts or screws holding it.
- Note the orientation of the old filter before removing it.
- Firmly pull the old filter straight down to remove it.
- Install the new Mercedes transmission filter, ensuring it is properly seated in its position.
5. Draining the Torque Converter:
- The torque converter is located towards the front of the car, in front of the transmission pan, within an oval-shaped housing.
- Locate the torque converter drain plug. It may not always be positioned at the bottom.
- If the drain plug is not accessible, you will need to rotate the engine to bring it into the down position.
- To rotate the engine, use a 27mm socket and a long breaker bar on the crankshaft pulley nut. Gently rotate the engine clockwise. Important: Do not attempt to loosen the crankshaft pulley nut itself, only rotate the engine.
- Once the torque converter drain plug is in the down position, use a 5mm hex socket with an extension to remove it.
- Drain the fluid from the torque converter. You should get another 3 liters of old fluid.
6. Reassembly and Refilling:
- Install new drain plug washers (if recommended) on both the transmission pan and torque converter drain plugs.
- Reinstall and tighten the torque converter drain plug to approximately 20 ft/lbs.
- Reinstall the transmission pan with the gasket (reusing the original gasket is often acceptable if it’s in good condition – rubber gaskets are generally durable). Tighten the pan bolts to 106 inch pounds (approximately 9 ft/lbs) in a crisscross pattern to ensure even sealing.
- Lower the vehicle off the jack stands.
- Locate the transmission fluid fill tube in the engine compartment.
- Using a long neck funnel, slowly pour in approximately 6 liters of new Mercedes-Benz approved transmission fluid into the fill tube.
7. Checking and Adjusting Fluid Level:
- Start the engine and let it idle in Park (P).
- Allow the transmission to warm up. You can monitor the transmission pan temperature with an infrared thermometer.
- Once the transmission fluid temperature reaches approximately 80 degrees Celsius (check specific temperature for your model – often between 80-85°C), remove the cap from the transmission fill tube.
- Insert the Mercedes transmission dipstick tool into the fill tube until it bottoms out.
- Remove the dipstick and check the fluid level. The fluid level should be at the upper mark corresponding to 80°C on the dipstick.
- Add more Mercedes transmission fluid as needed to reach the correct level. It’s better to add fluid gradually and re-check the level.
- Once the fluid level is correct, remove the dipstick tool and replace the fill tube cap.
8. Final Checks:
- Take the vehicle for a short test drive to allow the transmission to cycle through all gears.
- Re-check the transmission fluid level after the test drive, ensuring the temperature is still around 80°C.
- Inspect for any leaks around the transmission pan and drain plugs.
Tips for a Successful Mercedes Transmission Fluid Change
- Use the Right Fluid: Always use Mercedes-Benz approved transmission fluid that meets the specific requirements for your 722.6 transmission. Using the wrong fluid can cause serious damage.
- Temperature Matters: Accurate fluid level checking is temperature-dependent. Ensure the transmission fluid is at the correct temperature (typically 80°C) when checking the level.
- Cleanliness is Key: Work in a clean environment and use clean tools to prevent contamination of the transmission system.
- Don’t Overfill: Overfilling the transmission can be as detrimental as underfilling. Add fluid gradually and check the level carefully.
- Dispose of Old Fluid Properly: Dispose of used transmission fluid responsibly according to local regulations.
Conclusion: Maintaining Your Mercedes Transmission
Changing your Mercedes transmission fluid is a vital maintenance task that can significantly extend the life and performance of your vehicle’s transmission. While it requires some mechanical aptitude and specific tools, this DIY guide demonstrates that it is a manageable task for many car enthusiasts. By following these steps and taking your time, you can ensure your Mercedes-Benz continues to provide smooth, reliable performance for years to come. Regular maintenance, including Mercedes transmission fluid changes, is an investment in your vehicle’s longevity and driving pleasure.
