This is more an annoyance than a problem, but my driver's side window won't fully close unless I am stopped or going very slow. The truck is 2001 F-150 5.4L. If I try to roll the power window up while going down the highway, it will stop just short of seating good against the seal. I can crank it up and down all I want, but it almost never seats fully when I am driving. 'Course then it makes a wind whistle noise. If I am at a stop sign or just creeping along, however, it will seat itself with a solid 'thunk'.

What could be causing this? 'Been like this for years.