2008 6.4 PSD 83,000 miles. Been running the spartan 275 tune for a little over a year now. Was driving down the highway at 70 mph when I started to notice a loud howling / whining noise that seemed to match the rpm of the truck under power. Sounds like it is coming from right underneath the floorboard.... probably the transmission or TC? Im runnin 37 toyo mud terrains and the noise is quite a bit louder than the road noise of the tires. Then, when braking, or coasting I noticed the sound changes to a shuddering sound (like driving over road reflectors) and puts off a corresponding vibration to the floorboard. If i put the truck in tow/haul mode the noise and vibration is louder when coming to a stop. Seems to be running at a higher rpm at highway speeds than before. I have checked all drive train components, bearings, suspension. Tranny fluid looks good, not burnt. Haven't pulled the plug to check for shavings yet. Anyone had this happen to them, or know whats going on before I start throwin money into this thing? Ive been leaning on the torque converter going out, but not sure.