Tachometer issues can’t figure out the cause.

I have a 2002 Ford Ranger Edge 4.0l V6 engine. Has 231k miles on it. Recently I’ve noticed the tachometer acting strange. When the engine is cold or warm the RPM reads normal, even used a solus scan tool to see the idle is good, but RPMs suddenly will go up then back down but idle is constant. When driving I’ve noticed it will shift normally and the gauge will show normal 2.5 to 3k range to shift , stay up in that range after the shift or jump up even higher even though the shifting is completed, for a minute or so then suddenly drop to show the normal range. The thing that is I’ve also just recently noticed today, that it is little hesitant around 45 to 50miles when it comes to shifting, the RPMs show the shift around 3k but once the shift is complete it drops suddenly down to normal range. I’ve replaced throttle body and sensor, IAC valve and have cleaned Intake. Not sure if it’s a sensor in the cluster that controls the tachometer gauge or if it’s a transmission issue. Any ideas?