I have a 2018 68RFE in my Dodge Ram 2500 Cummins turbodiesel. It is low mileage and running well; but when decelerating with just a gentle touch of the accelerator, a "shushing" sound that sounds like TV static comes from the transmission. It goes away as soon as any load is applied, or the brakes applied. I suspect it is normal gear noise due to the transmission components moving in a no-load state. What do you think?