MacGyver doesn't need reverse and neither does the guy in the above video. His Nissan Pathfinder had a broken transmission and wouldn't shift into reverse. Short on funds, he chooses to engineer a cheap way to get by before having to cough up the money for expensive repair work.
By having the tires turn the PVC pipe like a cog in a machine, he's able to produce a reverse motion, albeit at a very slow rate. But, hey, if it gets the job done, it gets the job done.
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