2005 Chevy Avalanche error codes

The one code is a low inputknock sensor whic hcan be from not driving right due to the trans problems. I think this may all relate to the speed sensor especially since you are saying you have problems with the speedo. Either that oryou have connection problems at the speedo sensor. That would also throw off all your trans stuff like TCC control ad shfit control which are the other codes. The only way you can check the speedo sensor is to see if you are getting voltage to it and whether it is in the right ohm range. Of course if you've hit something on the road you could have broken wires at the harness by the transmission as well.