When a car jerks while changing gears, it means that the transmission is malfunctioning. There are several different reasons a transmission fails to work correctly. For example, low transmission fuel and a leak in the transmission both cause a transmission to malfunction. It is also possible that a transmission is worn out and needs to be replaced.
The first thing to check if a car jerks when gears are shifted is the transmission fluid level. Next, inspect the transmission to see if there are any leaks. Check spots such as the filler tube base, the drain hole underneath the transmission and the selector shaft. These spots are the most common areas that leaks occur. Also check underneath the car for fluid puddles.
The last thing to check is the transmission filter. When particles clog the filter, the transmission fluid becomes restricted. This can cause a car to jerk when the gears are shifted. Soak the filter in warm water and dish soap for at least an hour. Then gently run water through the filter until all debris is removed. If the filter is clean and there are no leaks, the transmission is most likely worn out and in need of repair.