Ok so this is the first time I've experienced this.

Speedometer didn't work, and car was stuck in first gear.

It corrected itself fairly quickly and I didn't experience the issue again.

Is this a sign of something?

 

Could be a low voltage, battery issue.

 

I don't think so! 14.4-15.2 usually. 2 batteries. But I'll keep an eye on stuff.

 

Then check ground wire , cluster fuse and for loose connectors

 

at the transmission?

 

The output speed sensor on the transmission tells the TCM when to shift and the speedo. My guess is a wire is loose or compromised.

 

Yes, at the transmission