High revving gear change

[Defect]

I have a VS Commodore and it seemed to be changing gears at a higher rev than normal. It was suspected that maybe the torque converter had been changed. The entire gearbox was replaced and the 7HDD box was replaced with a 6HDD box. Now it revs even higher than before. I'm not sure what the problem might be. Anyone have any ideas what might be the problem?

 

[seq4x4]

Checked coolent levels? The plug in properly? Your power button is on? Done an error code check?

I run a 6HDD in place of my 7HDD and never had a problem like that, but i drive like a twat and it rarly shifts at slow speeds for me to notice if and when it does.

 

[Defect]

The coolent levels are all good and the plug should be all good also. Haven't done a error check yet, how do I go bout doing one?
Also is there any chance that maybe the computers have been messed around with or even replaced?