1. Expression：in cahoots

Explanation： Often secretive or conspiratorial cooperation with someone. （秘密地，阴谋地与他人合作，相互勾结，狼狈为奸）

Usage：表示与某人相互勾结，狼狈为奸，在短语的后面用介词with，即：in cahoots with someone。

Example：It turned out that the business tycoon was in cahoots with local law enforcement to have the investigation dropped.

原来，这名商业大亨与当地执法部门串通一气使得调查终止了。

We've been in cahoots with a company overseas who can produce the product for half the price.

我们一直和海外的一家公司秘密地合作，他们可以半价生产这样的产品。

The mayor is in cahoots with the construction company that got the contract for the new building.

市长和那家可以得到建新建筑物合同的建筑公司彼此勾结在一起。

The mayor's enemies spread a rumor that he was in cahoots with gangsters.

市长的仇人散布谣言说，市长与歹徒暗自勾结。

2. Expression：in high gear

Explanation：operating at the highest, fastest, or most efficient level. （全力进行，全力以赴）

Example：We've expanded our development team and are in high gear working on our next project.

我们已经扩大了我们的开发团队，并且正全力以赴地进行下一个项目。

Construction is in high gear all around the city as it prepares for the upcoming Olympics.

我们在为即将到来的奥运会做准备，正全力进行着整个城市的建设。

A: When the interviewer asked me about my future plan, my head began to work in high gear. My talk was not long but hit the nail on the head, which made the interviewer quite satisfied.

当面试官问我未来的计划时，我的大脑开始极速运转。我说的并不长，但是说到点子上，这让面试官非常满意。

B: Congratulations! This time you are sure to succed.

祝贺你！这回，你一定会成功。

Explanation 2：of a vehicle, operating at a high or the highest gear. （指车辆以最高的速度运行）

Example：The car started to stall going up the hill and I realized that it was still in high gear.

汽车在上山时熄火了，但我觉得它仍然是以最高速度在运转。

You can't start out in high gear. You must work up through the low ones.

你不能以最高速起步出发，应该逐步加速。