when I accelerate from a stand still the vehicle will begin its shift cycle-1 to 2, but when it goes to shift from 2 to 3 it bears down and bucks before shifting. chevy says nothing is wrong i think they are full of it. if you place the vehicle in 2nd and try to drive when you give it gas it resists nad then bucks forward after enough stress nad drives the way iot shoud. this isnt not normal but i dont no why it is doing it and chevy wont help me. anyone have any ideas ????