While driving back from the place that sells truck caps, I finally quantified a feeling I sometimes get in my gas pedal.
At about 61mph to something over 65 but under 70mph, there's this rhythmic feel, like a cylinder about half covered with sandpaper. About once a second, the sandpaper passes beneath the gas petal. Does that make sense? A rough feeling that comes and goes about every second. Definitely slower than tire rotation. Because it's in such a narrow speed band, I can't really tell if it speeds up when I do - it sort of fades away. The feel when slowing down doesn't so much fade, as just stop.
It's definitely not the road, though, I was on asphalt, and went from old to brand new with no change in the feel. Engine doesn't seem to care, doesn't sound any different.
Appreciate any feedback.
jmc