In fairness, I should be totally honest.
I had a phone call last nite from a buddy who reminded me about a Mildon GD he installed that made noise, AFTER I promised him it wouldn't.
Here is the poop.
I did the machine work, he did the assembly, of which he is more than capable. When he installed the GD, the mounting bracket that holds the idler gear comes down and and too the drivers side.
I've never seen it, but there is always a strange on out there.
On his particular install, the very tip of the idler bracket was touching the timing cover. And it DID make some noise. Fortunately, I've heard noise gear drives before, so I knew something was off.
He drove over and we pulled the front off the engine. It took me a bit to see the witness marks. Did a little massaging and it was quiet as a church mouse.
So...be careful when doing the install. You can have the mounting plate touch the timing cover and it will make noise. Make sure you have clearance and you are good to go.
Other than that, you should never hear it.