Honer, The chattering noise you describe may just be the torque sensor spring covers rattling.I have several rigs that have this chatter at certain RPM's.With the machine off,see if you can move the covers,if so,this is probably the chatter you hear with nothing to worry about.You should take a prybar resting it against the concave adjustment and hooking the back side of the rear torque sensor sheave and see if you have any up and down movement of the input shaft to the gearbox.Usually you will see some movement start to develop around 2000-2500hrs. If this is a problem then you will need to disassemble the torque sensor asy..You don't need to remove the clean grain elevator and it isn't that hard to take apart.Require about 30-45mins. once you have done it,but life is alot easier with a service manual. Hyper Harvest II