Mercedes W639 Rear Axle Differential Diff 2,923 Ratio A6393501814 WARRANTY

Listing details

The differential is sold with a 90-day warranty! It was tested before removal and is in full working order.

Mercedes W639 Rear Axle Differential Diff 2,923 Ratio is a specialized drivetrain component designed for the rear axle of Mercedes vehicles equipped with a diesel engine and an automatic transmission. It is responsible for the precise transfer of torque to the wheels and ensuring the gear ratio is correctly matched to the engine's characteristics. This is a solution for users who expect stable drivetrain performance and predictable vehicle behavior in daily operation.

Specifications and technical data

• SKU: A6393501814
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A6393501814
• Substitutable numbers: A6393501814, A 639 350 18 14
• Location on the vehicle: Rear
• Fuel type: Diesel
• Gearbox type: Automatic
• Category: Differentials

Technical characteristics and purpose

The presented differential is a rear axle drive component that works in conjunction with a drivetrain based on a diesel engine and an automatic transmission. The applied gear ratio provides a balanced compromise between acceleration dynamics and fuel economy, which is significant in both city and highway driving. The design of the differential has been engineered to operate under the demanding load conditions typical for W639 series commercial and passenger-delivery vehicles.

Its placement on the rear axle promotes driving stability, and the properly selected gear ratio translates into predictable vehicle behavior during load changes, towing, or driving with a full load. For the user, this means smoother drivetrain operation, reduced stress on the automatic transmission, and more consistent vehicle throttle response.

Benefits of using a 2,923 ratio differential

Selecting the correct differential gear ratio has a direct impact on the performance characteristics of the entire drivetrain. In this case, the 2,923 configuration promotes:

• maintaining lower engine RPM at cruising speeds,
• smoother cooperation with the automatic transmission,
• reduced noise and vibration in the cabin during steady driving,
• stable torque transfer under typical operating conditions.

For fleets, commercial vehicles, and cars used for long-distance travel, this means more predictable fuel consumption and reduced stress on drivetrain components. A properly selected differential ratio also helps limit unnecessary gear downshifts by the automatic transmission, which contributes to its durability.

Professional selection and vehicle compatibility

The differential in this offer belongs to the Differentials category, meaning it is a component strictly linked to a specific drivetrain configuration, fuel type, and transmission type. When selecting, it is crucial to match it to the engine version, vehicle purpose, and expected driving style. A properly selected differential allows for maintaining factory drivetrain performance parameters without the need for interference in electronics or control unit software.

To better understand the relationship between the axle ratio and vehicle behavior, it is worth consulting specialized materials. A detailed discussion of the topic, along with practical examples and an explanation of how to choose ratios for your driving style, can be found in the article Dismantled drive axles and differentials – how to choose gear ratios for your driving style. This is a useful source of knowledge for both mechanics and informed users planning a drivetrain component replacement.

Application in vehicles with diesel engines and automatic transmissions

A configuration designed for diesel units combined with an automatic transmission requires a differential with appropriately matched characteristics. Diesel engines generate high torque at relatively low RPM, and the automatic transmission operates based on precisely tuned shift points. Using the correct differential helps to:

• maintain the optimal engine RPM range at typical speeds,
• preserve smooth gear shifting without excessive "hunting" for gears,
• limit overloads in the drivetrain during starting and acceleration.

Such tuning is particularly important in vehicles operated in mixed city/highway modes, where load and speed changes occur frequently. Stable operation of the rear differential translates into greater driver comfort and more predictable vehicle behavior over the long term.

Condition, origin, and product group

The offered item is a used part, which in practice means the possibility of achieving a favorable cost-to-functionality ratio while maintaining the manufacturer's original design. For many users and workshops, this is a rational solution for drivetrain repairs, especially in the case of intensively used vehicles. The original design for the Mercedes brand ensures proper fitment to factory mounts and axle geometry.

If you are planning a comprehensive repair or upgrade of your Mercedes drivetrain and need other components from the same group, such as axle housings, complete differentials, or final drive sub-assemblies, check the available parts in the Mercedes Differentials category.

Support for modifications and tuning

Changing the differential ratio is often one of the stages of more advanced drivetrain modifications, especially when you are simultaneously planning to interfere with engine parameters. In such a case, it is worth approaching the topic holistically – taking into account both the engine's characteristics and the operation of the automatic transmission and the axle. Practical tips on safely increasing performance using used components can be found in the guide How to increase engine power: a practical guide to engine tuning with used parts, which helps to plan modifications in a consistent and well-thought-out manner.