Slipping/Chuging above 50 mph

[clayheart74]

I have a 2004 Excursion about 80k miles. I have noticed when at cuising speed above 50 mph, it feels like it slips or kind of chugs or bucks. Not really sure how to explain it. My first thought was an alignment/balancing issue but after more driving time I am pretty sure that is not the case. At the moment it is slight but does seem to be getting worse. The engine sound seems to be normal at the time as well. I have recently replaced the fuel regulator, both filters, and changed the transmission fluids. I have read another post with what sounded like a similar issue and most people were pointing towards the U joints. Planning a family vacation in a few weeks and want to know what I need to fix before heading out.