It sounds like you have an issue with the vehicle speed sensor (VSS).
The VSS is located on the side of the transmission (see diagrams below).
It measures the rotation of the transmission shaft and sends that data to the ECM and that gets converted to the speedometer reading.
First make sure that you are getting 8V power to the sensor. Check the connector for any corrosion or looseness.
If you have adequate power and the connection looks good then it is likely a bad sensor.
To replace the sensor you will have to take the single mounting bolt.
Here is a helpful video:
I have attached diagrams for your reference.
Please let me know of any questions.
Images (Click to enlarge)
Monday, September 20th, 2021 AT 12:06 PM