Is it a problem with the yikong yk4082 motor?

I thought before that it was because there wasn’t enough oil in the gearbox of my yikong yk4082 rc car, so the motor of the yikong yk4082 rc car got overheated due to too much load. Today, I took off the transmission shaft of the yikong yk4082 rc car. It’s super easy to push. But after the single motor of the yikong yk4082 rc car runs for a while, the motor shaft starts to get really hot.