TotalEnergies for classic automatic drives
Every year, more and more vehicles with automatic transmissions are sold. There are many different types of such transmissions, but classic automatics, i.e. systems consisting of a torque clutch, a set of planetary gears in series and a control module, still have a significant market share. TotalEnergies reminds us of their basic operating requirements and presents its state-of-the-art lubricant products from the FLUIDMATIC range intended for their servicing.
In automatic transmissions, the gear ratio change is automatic, i.e. without the driver's involvement. The change should take place at the optimum moment for the desired driving style and the flexibility of the respective combustion engine. Such transmissions typically have three to eight forward gears and one reverse gear (in some cases even two). Advantages of such designs include the absence of a clutch in the car, driving comfort, and the engine and transmission are hydraulically rather than mechanically coupled to prevent overloading. Disadvantages of automatic transmissions include higher friction losses, lower efficiency compared to mechanical transmissions, greater weight of the assembly and higher production costs.
In the last century, many different types of automatic gearboxes have been developed. In general, we can divide them into stepped and continuously variable transmissions (CVTs). The former include dual-clutch transmissions and the most common “classic”, i.e. hydromechanical stepped transmissions with rotating axles. In this article, we will focus on the "classic" solution. Such a gearbox consists of three sub-assemblies: a clutch or hydrokinetic gearbox, a planetary assembly comprising mechanical single planetary gears (with rotating axles) together with the gearshift elements (i.e. brakes and multidisc clutches), and a hydraulic, electronic-hydraulic or electronic-pneumatic control system.
Traditional automatic gearboxes
The transmission of power in classic automatic gearboxes is the responsibility of the torque drive in the form of a clutch or a torque converter. The disadvantage of the clutch is that only the speed is processed while the torque remains constant (e.g. when starting the vehicle). Therefore, a hydrokinetic transmission is used, which transmits and increases engine torque. It consists of:
- a pump rotor connected to an oil-filled housing,
- a steering wheel rotor with a one-way clutch,
- a turbine rotor connected to the input shaft of a planetary unit.
The right automatic transmission oil must ensure that the pump, steering wheel and turbine work together properly, which determines maximum vehicle performance, minimum efficiency and driving dynamics.
The planetary assembly is made up of interconnected individual planetary gears, consisting of:
- a crown heel (with internal toothing),
- a sun wheel (central),
- several satellites mounted on axles and connected by a basket (yoke). Connected together, the individual planetary gears form a planetary series. By using different ways of connecting the individual segments (satellites, crown wheels, sun wheels), different gear ratios can be obtained.
Depending on the type of connection, Simpson, Ravigneaux and Lepelletier planetary series are distinguished. Brakes and multi-disc clutches are responsible for changing the transmission ratio, which respectively lock or couple the individual components of the planetary series. The right automatic transmission oil should provide an adequate film between contacting components, cooling, contamination removal and corrosion protection.
Should I change the oil or not?
One of the most frequently discussed service issues is the subject of oil changes in automatics. While in the case of CVT and dual-clutch transmissions, the service procedures are indisputable and depend on the type of transmission (with dry or wet clutch), in the case of classic automatics, the oil change technique is controversial. There are two ways to do this - basic and dynamic. In the latter case, the idea is to circulate the old and new oil while the power train is running, so that, like a "blood transfusion", as much of the old oil as possible is replaced by the new oil. With a classic exchange, a great deal of old oil remains in the transmission because it cannot be drained completely. Proponents of dynamic exchange say that it is the only sensible way to extend the life of the gearbox. Opponents point out that dynamic change is the best way to... damage the gearbox by clogging its sensitive channels with contaminants that have peeled off from other “safe places” such as the case walls.
Experts in the servicing of "automatics" favour a common-sense approach to this subject. If someone has been using an "automatic" since new and regularly changes the oil in it, a dynamic change will be the best solution. A person who buys an old, neglected car with high mileage should rather settle for a classic change....
TotalEnergies oils for automatic transmissions
FLUIDMATIC LV MV: high-quality automatic transmission oil made with synthetic technology for very smooth gear changes and fuel economy thanks to its low viscosity.
Oil change intervals are always specified by the manufacturer. Where data is not available, average values can be taken. In the case of automatic transmissions, this is between 60,000 and 150,000 km (occasionally transmissions with non-changeable oil are encountered).
The oils for automatic transmissions must have low viscosity (
A very good new generation oil from the TotalEnergies range for automatic transmissions is, for example, FLUIDMATIC LV MV. It is a high quality automatic transmission oil made using synthetic technology providing very smooth gear changes and fuel economy thanks to its low viscosity. It is suitable for modern automatic transmissions from most manufacturers. It is not a product with many official manufacturer approvals. However, it is suitable for a number of existing automatic transmissions on the Polish market. It is best to check whether it can be used for a particular transmission by reading the technical data sheet: FLUIDMATIC LV MV.
Common to all automatic transmission oils are very high requirements for friction modifiers that react with the friction plate surface. They must have adequate static and dynamic friction coefficients to prevent slippage while guaranteeing rapid gear changes. In addition, these oils must have low viscosity and a very high viscosity index to ensure that the gearbox functions properly at low temperatures and just as well at high temperatures. It is important that the oils also have good anti-wear properties to protect the gears, as well as suitably selected polymers that will not be subjected to shearing by the "agitator", i.e. the torque converter. This coupling also forces the oils not to foam. Andrzej Husiatyński, Technical Department TotalEnergies Marketing Polska