I am about to do a complete tear down and I see if I can't create a new mechanism for a belt drive and get rid of the gear drives all together.

No I haven't run it while warm and then increased the speed. I will try that today.

Having them too tight is a problem. It increases wear. It could be the source of the knocking in the gear box, I don't know I will see after the tear down.

Thanks for the response.