May be normal, but.....
I have an '06 250 powerstroke. I've noticed that when the tranny shifts into overdrive there is a pretty good vibration and a loud sound. I can feel it in the floorboard. This also happens when i'm in tow haul mode pulling my 12,000 lb. 5th wheel. It seems to do it the whole time in overdrive. Whether i'm teetering on the edge of going out of overdrive or whether i'm running 65 mph. Is this normal for a diesel or is there something i should be checking for? Thanks in advance for any help.