Deere 670B Noise at “high” speeds

So this motor grader DW670BX552951 came in and I have confirmed it does make a chain rattling noise on the left side tandem while running down the road in 8th gear. Opened up the inspection covers and the chain seems slack to me and oil level is 3.5" from the bottom of the tandem. All I can find is the oil should be 5 gallons capacity. I cannot find any specs in our literature on chain slack measuring, anyone know what that spec is and how JD wants it measured? Or if that is even the issue, Since its really only noticeable at 22+mph you pretty much have to be in 8th and it still makes the noise if I step on the clutch.