Q: RPMs rev but less mph daily. Eventually only went in 2nd gear 5 mph and then stopped going eventually.

Hello. From what you describe it would appear that your vehicle may be experiencing more than one issue. In order to determine if the issues are related I would need to know specifics such what sensor was replaced and if there was any trouble codes. Overheating is usually caused by issues with the cooling system. However, there are cases where engine performance or fuel issues can cause the engine to overheat. From what you describe it appears that whatever issues were present eventually put the vehicle in limp mode.

Limp mode is activated when the computer detects an issue with the engine that may potentially cause harm to the engine. The computer will drastically reduce power to the engine in order to prevent damage from occurring. It may also be possible that the issue is related to the transmission, perhaps in the form of a worn clutch disc, that is no longer able to engage the gears properly. As there appears to be many possibilities, I would recommend having a professional technician inspect the overheating issue and loss of power so that these issues can be resolved properly.