When slowing down either coasting or with brakes, I have a low noise that is definitely rotational. It kind of reminds me of mud tires but I don't have mud tires. I do have some mild cupping on the front and was going to get the alignment check and rotation this next week. Truck has 196000 miles on it. Has a ton of new parts over the years and most seals have been replaced and filled with synthetic fluids. Transmission is only 1 year old on the rebuild. Noise does sound like it is coming from below me but I have hearing damage from an explosion so my sound direction is often off. My wife can hear it too but she says the same thing. I first notice it around 40 MPH and lower. I don't detect any vibration either. I never hear it when I am accelerating but the truck is loud so it may be there, but you can't hear it over the cummins. We took a video of the drive shaft and it has some play that I don't know if that is normal. It is in the bushing after the transmission. I am told by my Chevy neighbors that would not be good on a Dmax. One last bit of information is the shocks are coming close to 80k miles on it. Not sure that matters.