Let’s continue the oil theme and talk about the transmission – about the nuances of replacing the working fluid in automatic transmissions and variators.

1. How often to change transmission fluid

Is it necessary to change it at all? The operating manuals of many modern cars claim that the transmission fluid does not require replacement and is designed “for the entire service life.” And this is true, it’s just that the service life of the gearbox will be very short.

Like any oil in vehicle components, transmission fluid becomes contaminated with wear products during operation, oxidizes, and loses its properties. This leads to accelerated wear of clutches, overheating of solenoids, the appearance of jolts and jerks, and as a result, a significant reduction in the service life of the gearbox.

The real service life of transmission fluid: 40,000–60,000 km for automatic transmission and 30,000–50,000 km for CVT. If you periodically tow a trailer, skid, or start uphill, focus on a lower mileage value.

2. Complete or partial replacement

Most services will offer you a hardware replacement of the transmission fluid, which allows you to renew it almost completely. This is a good way if the box is not too old and at least occasionally serviced.

But there are special cases – old cars with high mileage, the transmission fluid in which has not been changed from the factory. Hardware replacement of fluid under pressure can cause harm: raise a suspension of deposits accumulated over the years inside the box and clog the valve body. In such a situation, it is better to perform several partial replacements: drain the old fluid, add the same amount of fresh fluid, drive a little and repeat the procedure.

3. How to choose transmission fluid

Working fluids for different types of transmissions differ significantly. Fluids for classic automatic transmissions (ATF) contain anti-seize and anti-friction additives that protect the planetary mechanism. In additive packages for CVT fluids (CVTF), the emphasis is on friction modifiers and anti-foaming to prevent slippage and overheating of the belt.

But even for the same type of transmission, fluids differ – not only in additive packages, but also in viscosity. Old automatic transmissions and first-generation CVTs used thicker fluids that provided reliable lubrication at low speeds, but led to power losses. Modern transmissions use low-viscosity fluids to improve fuel efficiency.

It is important that the transmission fluid has the tolerance recommended by the car manufacturer for your gearbox. We have discussed the different types of fluids in more detail using the example of ATF and CVTF Masuma .

4. Do I need to change the filter?

In most automatic transmissions, the filter is installed inside the housing and is accessible only by removing the pan, and some models require complete disassembly. However, it is necessary to change the filter – its contamination worsens the circulation of the fluid, which negatively affects the operation of the transmission and its temperature regime.

Sometimes there is no transmission filter from the factory, but the manufacturer has provided a place for its installation on the gearbox housing, covered with a plug. In severe operating conditions, it is better to install a suitable filter yourself – this will extend the service life of the transmission.

There are almost 400 types of transmission filters in the Masuma line, we talked about them in this post .

5. How to set the liquid level correctly

The level of the working fluid is critical for the transmission: even a small deviation from the norm can lead to incorrect operation. The fluid level is checked differently for different gearboxes – but always with the engine running, so that the transmission fluid circulates and does not flow into the gearbox housing.

• Boxes with a dipstick : the level is checked on a warmed-up transmission (usually after 15-20 minutes of driving). The car is placed on a level surface, the selector is switched through all modes and returned to “P” or “N”. Then the dipstick is pulled out and the fluid level is checked at the “HOT” marks.
• Boxes without a dipstick : a control plug in the transmission housing is used. The testing procedure is more complicated: the liquid is heated to the temperature specified in the service manual (it is controlled using diagnostic equipment), then the plug is unscrewed. Intensive leakage indicates excess liquid, no leakage indicates a deficiency.