I was just wondering if anyone else has encountered this on an '04. My '04 S-Crew Lariat that I've had for a couple of weeks really lugs around 55-60 mph. So much so, that there's repititious vibration in the engine/transmission. As soon as you get up to 70 mph or thereabouts where the RPMS are higher, the vibration goes away. At 55-60 the RPM's are pretty low, say around 1500, maybe even a tad less. Are any of you guys having the same phenomenon? I know that it's a result of the gearing, I was just curious if you guys are living with it or what?