Speedometer and Shifting Problem?

Hello, my dad's 2008 I6 Trailblazer RwD Automatic just had the transmission rebuilt a month or two ago and now it's having issues. The speedometer isn't working, and he said it's shifting rough or not shifting into higher gear.

We replaced the transmission speed sensor because it was the easiest and cheapest to start with. Didn't work. We checked fuses and they're all good.

What other sensors might there be? Is there an internal one for this transmission? Could it be a wheel speed sensor? All other gauges on dash are working fine.

Thanks in advance!