Now that I have my catastropic failure addressed, another thing I noticed on my recent trip is that at about 70mph, I start getting a vibration, it's a very slow one compared to speed. Kind of a whump every second or two, on and off. Doesn't go away completely in between but kind of winds up more every other second or so. It's not a horrible truck is gonna fall apart one, but it was enough to keep me below 70. Last time I did any highway driving over 70 was a few months ago and definitely didn't have it then. Truck is an 89 K3500
454 th400.Thanks in advance, Ed