This is an interesting video explaining the importance of drive shaft angles and phasing. Phasing will be built in in original, one-piece drive shafts but it can be messed up in two-piece shafts with a slip joint in the middle.
Its amazing that I didn't have a vibration in a drive shaft I made by splicing ends of two different ones together.
https://youtu.be/gmV4qwLfOMY
Drive Shaft Angles and Phasing
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Drive Shaft Angles and Phasing
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