Possible causes of a jolt when stopping with an automatic transmission:
* Faulty torque converter: Provides a smooth connection between the engine and transmission. A faulty torque converter can cause shock when downshifting.
* Worn friction linings: provide engagement between gears of the gearbox. Worn pads can slip, causing shock.
* Low or contaminated transmission fluid: Lubricates and cools transmission parts. Low or contaminated fluid levels can cause increased wear and shock.
* Faulty sensors or electronics: Sensors provide information about the health of the engine and transmission to the electronic control unit (ECU). Faulty sensors or ECUs may issue incorrect commands, resulting in jerking.
* Mechanical problems: Worn bearings, synchronizers or other mechanical components can cause a jerk when downshifting.
* Faulty solenoids: The solenoids control the hydraulic passages in the transmission to change gears. A faulty solenoid can result in harsh gear changes.
* Timing belt or chain slippage: Imprecise ignition timing can cause shock during downshifts, especially at high engine speeds.
What you can do:
* Check the level and condition of the transmission fluid: low level or contaminated fluid should be replaced.
* Scan for trouble codes (DTCs): this will help identify faulty sensors or electronics.
*Refer to a qualified mechanic: Diagnosis and repair of mechanical or hydraulic components of the transmission may require special equipment and experience.