Not sure if it is original one or not. Looks like the bushing has finally given up the ghost. It is worn to the point that the misalignment of the tensioner pulley was positioning the belt about 1/8" off at the front. I don't know if it has ever been changed or not. Being the frugal type that I am I reached into my spare parts bin and got one that looks like it probably came off of a early 90's 300D. The pulley position is a little further from the rotation point on the older version. Belt seems to be fitted properly but the shock does look like it is closer to the end of its travel.

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Jim

If the big pin bolt is smooth - get a replacement arm, the old style wont properly work in your case.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)