What Causes Automatic Transmission Car Shaking When Shifting Gears?

[HenryMarie]

Automatic transmission car shaking when shifting gears is caused by: 1. Low idle speed; 2. Dirty throttle body; 3. Dirty fuel injectors; 4. Severe engine carbon buildup; 5. Poor spark plug performance. Automatic transmission means the driver doesn't need to manually shift gears - the vehicle automatically selects the appropriate gear based on driving speed and traffic conditions. The method for shifting gears in an automatic transmission car is: 1. Start the vehicle in P or N gear, shift out of P gear while holding the brake, turn on power while holding brake and shift to N gear, then shift to D gear after ignition to move forward; 2. No need to press the shift button when switching between N, D and L gears, press the shift button when shifting from L gear to lower limit gears, no need to press shift button when shifting from lower to higher gears; 3. Do not shift to N gear while driving to coast; 4. After driving, turn off the engine and shift to P gear before removing the key.

[LaMargaret]

Automatic transmission gear shaking is quite common. Once when I was waiting at a red light in D gear, the car shook like a phone vibration. Later inspection revealed that the engine mount rubber pads had aged - once the rubber cracked, they lost their damping function. Also, if transmission fluid hasn't been changed for too long, reduced viscosity will worsen gear shift jerking. I recommend checking engine mount conditions every two years - rubber components need replacement every five years or so. Excessive carbon buildup in the throttle body can also cause shaking, especially for city stop-and-go vehicles - cleaning every 30,000 km suffices. Spark plug gaps being too large similarly affects power transmission - I've seen cars shaking like massage chairs that immediately quieted down after installing platinum spark plugs.

[DePenelope]

Attention to automatic transmission drivers: Gearshift vibrations are often related to these three key areas. First, the engine mounts—the rubber buffers between the engine and frame—transmit vibrations when aged. Rubber components harden and crack after 5-6 years. Second, transmission fluid condition: if unchanged beyond 60,000 km, reduced lubrication increases planetary gearset friction during shifts. Lastly, throttle body carbon buildup—like sludge clogging pipes—restricts airflow, causing RPM fluctuations and vibrations. Regular maintenance is crucial: inspect transmission fluid every 40,000 km, replace air filters annually to prevent dust ingress, and shift to Neutral at traffic lights to reduce engine load.

[SanGabriella]

I've experienced gear shift shuddering firsthand. Common causes include deteriorated engine mounts reducing vibration absorption, allowing engine tremors to directly transmit into the cabin. When spark plugs misfire, causing unstable cylinder operation, the tachometer needle will fluctuate. Dirty transmission fluid affecting hydraulic system pressure can also make shift mechanisms sluggish. Don't rush to repair when encountering shuddering - first conduct a test: repeatedly cycle through PRND gears after cold starts. If shuddering only occurs in Drive, it's likely an engine mount issue; if present across all gears, internal transmission problems may be the culprit. Minimize sudden acceleration in daily driving and shift to neutral when parked over 30 seconds to protect shift mechanisms.

[HarmonyLee]

Last time I helped my neighbor check his old Accord, it also shook violently when shifting to D gear. Eventually, we identified two issues: the right engine mount was completely broken, causing the engine to lose support and directly hit the chassis; the transmission fluid hadn't been changed for eight years and had turned black. Such shaking should be addressed early, or it may lead to more significant failures. For those with good DIY skills, you can inspect it yourself: open the engine hood, have someone shift to D gear while pressing the brake, and observe the engine's movement—if it exceeds 1 cm, the engine mount needs replacement. Also, don't overlook the fuel system; clogged fuel injectors can cause uneven air-fuel mixture and incomplete combustion, leading to shaking. Regular use of fuel system cleaners can help alleviate this issue.