RPM's suddenly drop while driving?

I drive a '98 Ford Explorer and recently the RPM's will suddenly drop while i'm driving. I will accelerate and the transmission will go through the normal gear cycle shifting at around 3-3.5k (sometimes it shifts at 2.5k) and once i reach a cruising speed and let off the gas a little bit, the RPM's drop to around 1800. It used to stay steady at around 2.3k while cruising so the sudden change is a bit weird. It will also feel like it's jerking a little bit when starting to accelerate, and it doesn't have as much power as it used to. Could this be a larger problem with the transmission, or are there other simple solutions to fix it?

Do you have any check engine lights? If so, start there. Or;

I'm just guessing here, but your computer may have something to do with it. It regulates transmission shifts, idle, etc…

Other thoughts are vacuum leaks, vehicle speed sensors (mounted on the transmission and related), throttle position sensor, and other electrical regulators/sensors, etc…

Sorry not sure, but hope these may give you some direction on where to look.