What Causes the Impact Sound When Accelerating or Decelerating the Transmission?

[ODavid]

Transmission accelerating or decelerating with an impact sound may be due to a clogged fuel line. Automatic start-stop systems paired with dual-clutch transmissions inherently have this issue. Abnormal ignition can also be a cause. Clogged Fuel Line: Clean the fuel line, fuel injectors, fuel lines, and fuel pipes. Adding fuel cleaner directly to the fuel tank is the simplest method, but the effect is not long-lasting, and the cleaning is not thorough. This method is suitable for vehicles with low mileage. Use the "drip bottle" method for cleaning. This can simultaneously clean carbon deposits and sediments from the fuel line and valves, and is commonly recommended by auto repair shops. Abnormal Ignition: Replace spark plugs or the ignition coil. Promptly charge or replace the battery to avoid insufficient power. Use engine oil suitable for the current temperature conditions. Increase the frequency of vehicle use to expel accumulated water in the exhaust pipe with strong exhaust force. Add antifreeze. Regularly clean carbon deposits from the valves. Remove dirt from the spark plugs.

[VonJosiah]

I recently researched transmission noise issues, where clunking sounds during acceleration or deceleration often stem from mechanical component failures. For manual transmissions, common causes include worn synchronizers creating gear clearance collisions during shifting. In automatics, it could be a damaged torque converter damping spring or unstable oil pressure. Don't overlook checking the driveshaft's universal joints - aging joints develop play that causes loud noises, and loose engine mounts can transmit vibration sounds. Long-term neglect of these impact noises accelerates internal transmission damage, potentially leading to roadside breakdowns and significantly higher repair costs. I recommend immediate diagnosis by a reputable repair shop rather than DIY attempts, as drivetrain systems are complex and hazardous. Regular transmission fluid changes reduce risks, as contaminated oil accelerates wear.

[DiAriana]

From my 20 years of driving experience, the impact noise during throttle application/release is truly alarming. That time when my car made severe noises on the road, it turned out to be either loose differential gears or a broken axle bearing. This type of sound often becomes noticeable during rapid acceleration or deceleration, and manual transmission cars can produce similar noises when the clutch doesn't fully disengage. If the noise worsens during turns, it likely points to a differential issue in front-wheel-drive vehicles. I advise you to document the noise pattern: whether it occurs during low-speed starts or after high-speed gear shifts, and whether the location is under the chassis or at the front of the engine. This helps mechanics diagnose faster. Safety first—don't push through driving when the drivetrain is failing, as handling may become unstable, especially during high-speed rainy conditions. Have it towed directly to a repair shop for inspection.

[OEverett]

Simple solutions for transmission knocking noise. First, check if the transmission fluid is sufficient or contaminated; poor-quality fluid in automatic transmissions can easily cause noise. Also, inspect for loose engine mounts that may cause overall shaking. For manual transmission cars, try pressing the clutch pedal—if the noise diminishes, it may indicate clutch wear. Don’t delay, as louder noises often signal worsening issues, such as increased universal joint play or bearing damage. Schedule a repair immediately—a technician can pinpoint the source using a stethoscope. Ignoring it may damage more components and increase repair costs.

[DavidDella]

This impact sound poses significant hazards. If left unaddressed, the transmission damage will worsen, leading to costly repairs. Moreover, the noise during high-speed driving can mask other warning signals, increasing the risk of rear-end collisions. Mechanical clearance issues, such as loose differentials or drive shafts, may cause loss of control on bumpy roads and affect braking response. I've seen cases where procrastination resulted in complete transmission failure. Safety should always come first—address the issue promptly to avoid complications. Have a professional shop conduct a comprehensive inspection of the drivetrain system.