Gear oil (transmission fluid) for your car

Your Gear oil (transmission fluid) worn out? » Read more about common malfunctions • Repair • Replacement manual

Smooth operation, low wear, safe driving Many motorists are familiar with the term 'oil change'. This usually refers to changing the engine oil. It is a bothersome task, but must be performed regularly. One thing that is often forgotten here: Wherever gears interact, proper lubrication is necessary. This also includes the transmission and the differential. Regularly changing transmission oil & axle drive oil Changing transmission oil is by far not needed as frequently as changing the regular engine oil. This is due to the lower operating temperatures and lesser strains in a transmission or axle drive. Furthermore, both assemblies are closed systems. Unlike the engine, in which an exchange of air and fuel takes place constantly, a transmission is a closed system. In normal cases, no foreign matter penetrates it. Here, the wearing of oil is mainly due to internal abrasion. Although miniscule, this becomes noticeable in the form of ever deteriorating lubricating properties. Yet, since the transmission oil must be drained anyways when replacing the clutch, it can be changed when performing this repair. What is the transmission and axle drive anyways? The manual transmission is the common transmission that is operated by means of a gear knob. It transmits the engine's rotational speed to the wheels. The torque that reaches the wheels depends on which gear is selected. The technical difference between an axle drive and a manual transmission is that the axle drive has a fixed gear ratio. The most well-known axle drive is the differential gear. On rear-wheel drive and all-wheel drive vehicles it is located on the rear axle. It transfers the force from the front engine to the rear wheels. Here, in addition to increasing the torque, the direction of the force is also changed. The torque coming from the engine is diverted by 90° to the drive wheels with the help of bevel gears. When to change transmission oil & axle drive oil? It is recommended to change the transmission oil every 80,000-100,000 km. Obsolete oil is noticeable by a characteristic whistling noise coming from the transmission. Furthermore, changing gears becomes far more difficult. Switching to some gears can also become entirely impossible. In modern vehicles, a failing transmission can trigger the emergency program. If this happens, a visit to the workshop is inevitable. The need to change the transmission oil can also become noticeable due to loud noise. But since this noise only emerges gradually and slowly, it can go unnoticed for a long time. Although an axle drive is rather simple from a technological viewpoint, it is usually very expensive. Therefore, one should adhere to the prescribed oil change intervals. One important thing regarding the oil change intervals is checking the vehicle's current mileage. A general rule that applies to transmission oil change intervals is that they keep being spread apart further until reaching about 80-100,000 km. The transmission must be "broken in" at first. Therefore, it is quite likely that the first recommended change intervals already become due after 15,000 and 40,000 kilometers. Beware of Longlife! The premium manufacturers BMW and MERCEDES-BENZ provided no maintenance intervals for transmission oil & axle drive oil in the mid-90s. The reason for this was the ostensible unlimited confidence in the newly developed Longlife oils. In practice, however, it is evident that all types of oil age. Therefore, we recommend changing the transmission and axle drive oils upon reaching a mileage of 80,000 km, even if not required by the oil change intervals. The cost of fixing major damage to the transmission or differential is disproportionate to the cost of an oil change. Make no compromise All sorts of miracle products pertaining to the transmission and its lubrication are being advertised. This includes the so-called "stop leak" additives. Their use is not recommended. If oil seals or housing seals fail on a transmission, you should always repair them properly. In the worst case, additives not prescribed by the manufacturer can do more harm than good. How much transmission oil & axle drive oil? Many shy away from changing the oil because it is significantly more expensive than regular engine oil. It is nonetheless advised to only use the types approved by the manufacturer. A liter of oil costs about EUR 10.50 - EUR 15.00. Here, too, brand quality (Castrol, Liqui Moly) is preferable. There isn't really a defined axle drive oil. However, the exact types of oil that can be used for the differential gear are prescribed in the manufacturer's maintenance instructions.