- poor-quality engine adjustment;
- poor-quality adjustment of the gearbox;
- malfunctions in the hydraulic system of the gearbox;
- malfunctions in the mechanical system of the gearbox;
- malfunctions in the computer or its electrical circuit.
First of all, check the level and condition of the oil in the gearbox and the adjustment of the rods, and on models before 2001, the adjustment of the throttle control rod.
Preliminary control
Take a short drive to warm up the transmission.
Check the transmission fluid level in the gearbox.
If the fluid level is low, add fluid to the transmission and check for external fluid leaks.
If the fluid level is much higher than required, drain the excess fluid and check if there is coolant in it. The presence of coolant in the transmission fluid indicates that the internal walls of the radiator, which separate the transmission and coolant, have been destroyed.
If the transmission fluid is foamy, drain it and refill with fresh fluid.
Check the engine idle speed. If the engine is unstable, adjust the engine before performing further checks.
Check the freedom of movement of the accelerator cable, adjust if necessary.
Check the operation of the gear selector mechanism.
Check that there are no leaks at the gasket and o-ring locations in the gearbox.
Attention! The smell of burnt oil is a sign of contamination with small particles as a result of wear on the friction linings of the automatic transmission controls. This should alert you, as the gearbox may need to be overhauled.
Attention! If the oil level in the automatic transmission is below normal, air will enter the oil pump, resulting in oil foam. This in turn will cause a decrease in the operating pressure in the control system, slippage of the friction controls of the transmission and a delay in gear shifting.
Attention! If the oil level is higher than normal, then as a result of the rotation of the gears of the planetary mechanisms, abundant foaming will also begin, which will lead to the same consequences as in the case of a low oil level.
Attention! The formation of an air-oil mixture will eventually cause the oil to overheat and oxidize, which will adversely affect the operation of valves and friction controls. In addition, foaming will cause increased oil release through the breather, which can be mistaken for oil leaks from the system.
Diagnosis of transmission fluid leaks
The location of transmission fluid leaks is easy to determine visually. Repair usually consists of replacing gaskets, o-rings and cuffs.
If the leak is difficult to locate, follow these steps:
- identify the liquid. First make sure it's a transmission fluid leak, not engine oil or coolant. The transmission fluid is dark red;
- take a short drive, then stop the car over a large piece of cardboard. After a few minutes, by drops falling on the cardboard, determine the location of the leak;
- inspect the site of the suspected leak, paying special attention to the gaskets. Use a mirror to facilitate searching in hard-to-reach places;
- if no leak is found, clean the suspected area with a solvent and dry it;
- drive until the transmission warms up in various modes with gear changes, then re-inspect to determine the location of the fluid leak.
After determining the location of the leak, determine and eliminate its cause. If the gasket is being replaced, but the mating surface on which the gasket is installed is deformed or has scuff marks, then only replacing the gasket will not give a positive result. It is necessary to pre-level or clean the mating surface.