One possibility is that the transmission fluid level is low. When the fluid level is low, it can cause the gears to grind together when they shift, making a grating noise. You should check the transmission fluid level and add more if necessary.
Another possibility is that the transmission filter is clogged. A clogged filter can prevent the fluid from circulating properly, which can also cause the gears to grind together. You should replace the transmission filter according to the maintenance schedule in your owner's manual.
If the transmission fluid level is correct and the filter is clean, then the noise may be caused by a worn-out gear or bearing. In this case, you will need to have the transmission repaired or replaced.
Here are some additional things you can check:
* The transmission mounts: If the transmission mounts are loose or broken, it can cause the transmission to move around, which can make a grating noise.
* The driveshaft: If the driveshaft is damaged or loose, it can also make a grating noise.
* The differential: If the differential is damaged or loose, it can also make a grating noise.
