trans?

[Geoffmary]

Been having a strange problem somewhat intermittently with my '98 Expedition. While holding the gas steady at about 40 mph, the tach will fluctuate from 2000 to 3000 rpms. Any ideas?

 

[Richie Rich]

Had your fuel filter changed lately?

 

[Geoffmary]

If it were the filter, wouldn't the car slow down? The speed remains constant and it almost seems like the trans is searching for the right gear. It's been a couple years since I changed the filter, though.