Hi 6.7 Fan I have the same issue and I believe it happens when the exhaust cleaning message appears . It's like the truck starts dieseling, it shakes when going up the slightest incline starting at 45 mph. Even though the message goes away about the cleaning or drive to clean message you still don't know how long it last till the cleaning is finished. Never has it happened when traveling on the road during camping trips or long highway trips only around town when driving only a couple of miles a day it will start to happen when the messages begin.