问：汽车混蛋

My car is jerking when i brake hard or medium like if you come to a red light in a city ...for explain ....but it jerk right when the car is about to stop or right when it stops it's feel like two jerks in one (back to back) .it feels like shifting out of 2 into 1st seems off but it doesn't do it if i brake soft like granny driving.. i don't know .things I've done a tranmission flush, checked for warped breaks bad brakes,everything fine, I put I the car in neutral and braked hard like "hard" it did not jerk I'm just trying to figure out what else can cause this all fluids are fine and clean no metal no glitter , no engine light on

我的汽车有145000英里。
My car has an automatic transmission.