I only just realized that in my JD 7130 6 cylinder version which has a turbo that the turbo no longer does the high pitched whistle that is so common with turbos and is usually a tell tale that an engine has a turbo. It used to be really obvious even just driving along no under much load, like not more than any other turbocharged tractor just what you would expect and now I hear nothing and I know I can still hear well above that frequency because well I am 23 and have good hearing. No clue how long it has stopped making this sound and really I am no idea if this means anything about the turbo or if it just does not whistle as loud when it gets older? 2500 hours now on that engine which is not that much but still. I know the turbo is still spinning or at least part of it because I can hear it wind down when I turn off the tractor, I had the hood up checking fluids and I listened next to it and it is spinning for sure or at least the drive side is spinning for sure. But the tell tale whistle I am used to in a turbo charger is no longer there, does it mean anything or nothing? Also in my other post I asked about a flashing light and it is gone now, turns out the radiator was down a bit and there may have been some water in the fuel filter, I checked it all over and the light is gone so yay!.