Transcription: Four-wheel drive is a system that makes all four wheels driving wheels. There are many variations. Most primitive are part-time systems selected with a switch or lever. They connect all four wheels so all go at the same speed. Full-time four-wheel drive systems can stay engaged at all times if desired. They use a center differential or other device to manage the distribution of power to the front and rear wheels. When it senses impending wheel slip, it can lock itself temporarily. All-wheel drive systems work invisibly without the need to engage them separately.
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