I downshifted without thinking.

我毫不犹豫地就驶下去了。

She stretched out and down, and there was a sudden backwards thrust and the high squeal of torque as she downshifted a gear.

当她调至低档了一个工具的时候，她伸展出而且墬落，而且向后有突然推进和转力矩的高尖叫。