2001 Dodge Neon Shakes When Stepped On Brake On Third Gear.

I Have A 2001 Dodge Neon. And When I Put It In "Drive" And I Accelerate When It Changes To 2 or 3rd Gear And I Step On The Brakes It Starts Shaking. But If I Put It In "1" Or "2" It Works Fine. It Just When I Put It In "Drive" It Start Shaking After 3rd Gear And Step On The Brake It Start Shaking And Sometimes It Turns Off. Any Ideas What Might Be? Please Help. It has the Check engine light on. And when I put the little machine to see what number it is it come up with "P0743" and I look it up and it said its the Torque Converter Solenoid Circuit Electrical. But Im Not Sure. I Dont Think Its Thats Why It Shakes.