[mongocanfly]

You need a little angle in the ujoint to make the needles rotate in the cup to lubricate them...0 deg is not ideal..
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U-Joint Angles - U-joints need a slight angle for proper lubrication. Without the correct angles, the needle bearings in the u-joint caps do not rotate. Those needle bearings need to rotate in order for the u-joint to operate reliably and smoothly. These u-joint angles should always be at least 1-degree to avoid wearing out the yoke bearings. U-joints fail at 30* degrees.