It could be that the fluid level is simply low, but I would see if that rebuilt transmission is still under warranty. If so, take it back there. The problem, whatever it is, is likely inside the transmission. Transmissions are not my area of expertise, but I have got a good feeling that is what the problem is. Over the years I have seen enough "rebuilt" transmissions fail within six months because they are not truly rebuilt, but instead have had the one problem area fixed, and nothing else done that should have been done. In reality, these are simply repaired transmissions, not rebuilt.
Take a look at this guide:
https://www.2carpros.com/articles/automatic-transmission-problems
Here is how to check the transmission fluid level: Simply start the engine, and take the car around the block, or however far you can safely drive it. Then, with the engine still idling, raise the hood, find the transmission dipstick (probably red in color, near the back side of the engine) and pull it out. Be careful here, there are moving parts such as belts and pulleys that will snag pieces of hanging clothing/jewelry and do some serious damage. Clean the dipstick off using a napkin or something similar, and then reinsert it and pull it out again. The fluid level should be somewhere within the range that is indicated on the stick. If there is not enough, then go down to the local parts shop and get some fluid (I *think* this car uses Mercon IV or V). Pour it down the dipstick tube using a funnel. I am also attaching Ford's information on the subject in the images below. While my method and information is more general, this information is more specific. Let us know what you find.
Images (Click to enlarge)
Nov 11, 2018 at 8:18 PM
