my automatic transmission runs normal until 3rd gear than there is high revs and no forward power.
Check your transmission fluid level first. Top off and test if low. If the fluid level is full take note of the color. I like to use a paper towel and some fresh fluid to compare the color. If the transmission fluid looks burnt or dark, then you are looking at internal clutches burnt. Lets say the color is clean and looks good. Then you are most likely looking at a failed component such as a shift solenoid. Sometimes the computer will store a code that can indicate a failing sensor. A scan tool is required to retrieve these codes.