What Causes the Abnormal Noise When Shifting Gears in an Automatic Transmission?
4 Answers
Automatic transmission shifting produces abnormal noise due to the following reasons: 1. The release bearing lacks lubricant, causing dry friction or bearing damage. 2. There is no clearance between the release bearing and the inner end of the release lever. 3. Severe oil contamination or dust accumulation between the release bearing sleeve and the guide tube, or fatigue, breakage, or detachment of the release bearing return spring and pedal return spring, resulting in poor return of the release bearing. 4. Loose fit between the spline hole of the driven plate and its spline shaft. 5. Annealing, fatigue, or breakage of the driven plate damping springs. 6. Loose rivets or exposed rivet heads on the driven plate friction disc. 7. Wear and looseness of the drive pins of the double-disc clutch and the pin holes in the intermediate pressure plate and pressure plate.
I've been driving automatic transmission cars for many years and have encountered abnormal noises when shifting gears a few times. The most common reasons are insufficient or deteriorated transmission fluid. If the oil is old and sticky, the increased friction during gear shifts can cause a clunking sound. Another issue is severely worn clutch plates. Components inside the automatic transmission wear out over time, such as loose brake bands or misaligned gears, which can produce unusual noises. Additionally, unstable oil pressure can also be a cause, possibly due to a stuck oil pump or valve body. I recommend starting with simple checks—measure if the fluid level is adequate and check if the color is clear. If it's black, it's time for new oil. If that doesn’t help, take it to a repair shop immediately to avoid costly repairs later. Some cars have design flaws, like making noise when starting on a slope. In such cases, shifting gears more smoothly can help. Remember, regular maintenance is key to prevention, such as changing transmission fluid every 40,000 kilometers to avoid many issues.
As an automotive enthusiast, I've studied the working principles of automatic transmissions. Gear shifting noises are usually related to internal mechanical components, such as incomplete clutch plate engagement or damaged synchronizers, where increased friction between parts during shifting creates noise. Valve body blockage is another common factor - that component controls hydraulic flow, and once obstructed, pressure fluctuations can cause clunking sounds. It could also be due to faulty sensors or control modules, where inaccurate signals lead to rough shifting. I often remind friends not to ignore such issues; while the noise might seem minor, it could trigger a chain reaction, like wearing out gears and affecting the entire drivetrain. It's best to check for oil leaks under the chassis after parking, as aging oil seals can also be a contributing factor. From my experience, frequent gear changes in city traffic jams make these noises more likely, so driving habits matter too - gently pressing the accelerator can reduce impact.
Having driven automatic transmissions for over a decade, I firmly believe prevention is better than cure. Gearshift noises mostly stem from inadequate maintenance – for instance, delayed transmission oil changes lead to oxidation, causing insufficient lubrication and dry friction between components. Oil pressure imbalance is another common culprit, especially when valve body carbon buildup obstructs fluid flow, resulting in clunky gear changes. I recommend regular maintenance: change the oil every 30,000 kilometers while inspecting the filter for clogs. Avoid sudden acceleration and hard braking – smooth driving extends component lifespan. If noises already occur, first check fluid levels yourself; this simple step can resolve most issues. Stay vigilant about vehicle condition – neglecting minor symptoms often leads to costly major repairs.
