A silent killer of automatic transmissions or gearboxes is the mixture of water or coolant with automatic transmission fluid (ATF). This problem was observed in older vehicles with neglected engine cooling systems, but it is becoming common in the models of cars and trucks that have followed their maintenance programs. The result is always the same: the transmission must be completely overhauled or replaced.
Can the contaminated liquid be cleaned before the damage occurs?
Almost all automatic transmissions today use cellulose-based plates called clutches. or friction. These clutches act as brakes to move and stop different components inside the gearbox. When the shifter is turned on or in reverse, it is friction that is applied
The paper lining the clutch plates is a very delicate material that is glued to a steel spine. Before the paper is glued to the plate, it has the strength and consistency of a graham cracker. Once the material is glued, it becomes much stronger and can last a very long time under normal operating conditions.
The material of the clutch is hygroscopic. This means that when the clutches are exposed to moisture, the paper material moves the ATF to the water. This moisture reaches the steel plates causing rust, and breaks down the glue that binds the paper to the plate. A study by International Lubricants Inc. on the effects of water exposed to automatic transmission clutches, "The tests indicated that water added to levels as low as 600 mg / kg migrated to the surface of the water. untreated paper friction and contributed to paper loss coating properties and erratic torque transfer. "In simple terms, it means that less than a tablespoon of water or coolant in a transmission can cause a failure.
How did water arrive?
Water can enter a transmission in three ways:
- By the engine radiator. Since the 1950s, most automatic transmissions are cooled with the same water-based system that prevents the engine from overheating. There is a separate reservoir in the radiator for the transmission fluid that allows the coolant to remove heat from the ATF without mixing the two liquids. When a leak occurs between the ATF and the engine coolant tanks in the radiator, the fluids mix with each other. This was more common in older vehicles that had eroded cooling systems due to negligence, but some of the newer vehicles use materials that fail due to pressure problems in the cooling system . Driving through large puddles of water during thunderstorms or off-road can expose the respiratory system of the transmission to moisture. The best chance of preventing a failure is to check the water in the ATF after a vehicle has been in this type of scenario.
- Moisture entering by the gauge. Most vehicles have a gauge where the ATF is checked and added. Moisture can easily get into the transmission if the gauge has been sprayed with water while cleaning the engine, or in some cases, the water running off the rain or a car wash sinks on the dipstick. GM and Chrysler have bulletins for this problem on some models of their vehicles. Qualified stores will have access to check these types of newsletters. A telltale sign of this problem is moisture or rust around the gauge tube.
Replace or rebuild?
It depends on the amount of water mixed with the transmission fluid, the driving time of the vehicle with the contaminated ATF and the type of gearbox of your vehicle. The metal and electronic parts inside the transmission corrode quickly when they are exposed to moisture. If there is too much damage to the interior of the gearbox, the cost of parts to rebuild the trans will exceed the cost of replacing the unit with a remanufactured product. Some manufacturers like Nissan and Chevy have computers inside the gearbox that will fail when they are exposed to moisture. These computers or mechtronics cost up to $ 2,000 and this does not include rebuilding the rest of the unit. When parts cost so much, it's often a better decision to fully replace the gearbox.
In summary, if water gets into a gearbox, there is no way around a costly repair. Flushing the liquid will only cost you extra money and can make the inevitable failure sooner. Service the engine cooling system regularly and ask a professional transmission mechanic if your car is common for this type of failure. If this is the case, work around the radiator with an external oil cooler.