A timing gear starting to go bad will be noisy but pretty much undetectable
when the gear is removed from the engine (except perhaps oil seeping from
between the fiber part and the steel hub).
What happens is that the fiber starts to work loose from the knurled hub and
gets a very slight rotational play. In advanced cases it may even turn on the
hub under heavy load and then settle back into its correct location at idle.
Just about every oldtimer I have had has wiped a timing gear and most of them
looked OK when I removed them. And they all made the knocking noise.
--
George Downs Bartlesville, Heart of the USA!
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