Speedometer not working

If the speedometer is the only thing not working then we need to suspect the vehicle speed sensor is the issue. However, I am not sure I know what you mean by it "tries to shift down but it goes up and down lugs."

The way this works is the vehicle speed sensor sends its signal to the ABS module and then it sends the signal to the transmission control module and the PCM. Then the PCM sends the signal to the cluster to display the speed. So if it is the speed sensor we should have some codes. Have you checked for codes yet?

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If not, let's do that and go from there.

Also, if you have a scan tool we need to monitor the PCM while driving and see if there is a speed signal in the PCM. If there is, then the speed sensor is not the issue.