Why Are There Many Small Bubbles in Transmission Fluid?
2 Answers
Transmission fluid contains bubbles due to either excessively high or low fluid levels. When the fluid level is too high, planetary gears and other rotating components partially submerge in the transmission fluid, causing agitation and leading to bubble formation. Conversely, if the fluid level is too low, the oil pump may draw in air, mixing it with the fluid and generating bubbles. If these bubbles enter the hydraulic control system, the system's pressure may drop, affecting the transmission's normal operation and potentially causing slippage. Additionally, bubbles can cause the fluid level to rise, leading to overflow through the transmission vent or filler hole, which may result in misdiagnosis. Signs that indicate the need for transmission fluid replacement include: vehicle shaking, rough gear shifting; transmission overheating warning on the dashboard; engine stalling; and unusual noises. The methods for replacing transmission fluid are as follows: 1. Loosen the drain plug at the bottom of the transmission to drain the old fluid before refilling. 2. Remove the transmission oil pan directly for draining and refilling: This method is more thorough than the previous one, as it allows for the removal of debris from the bottom of the oil pan. 3. Use a circulation machine to replace automatic transmission fluid: Dynamic fluid replacement with an intelligent circulation machine can filter and clean sludge and impurities inside the automatic transmission. Hazards of not changing transmission fluid for an extended period: 1. Damage to the transmission's shift control mechanism; 2. Abnormal wear of gears and clutch plates inside the transmission; 3. Impaired transmission operation, leading to valve body damage.
The presence of a large number of small bubbles in the transmission fluid is usually due to air entering the oil. Having driven for many years, I've encountered this issue several times. The most likely causes are low fluid level, where the oil pump draws in air during operation, or aging/damaged seals allowing air to seep in. Checking the transmission fluid level is a simple step: wait until the car cools down and then inspect the dipstick marks. If the level is low, promptly top it up to the specified level; otherwise, bubbles will multiply, leading to insufficient oil pressure and poor lubrication. Prolonged neglect can accelerate internal gear wear, resulting in costly repairs. I recommend making it a habit to check the fluid level and quality every 10,000 kilometers or so to catch issues early. Never ignore this—safety first. I wouldn't want my transmission to suddenly fail on the road.
