Can I put a different size tire on my envoy than what came from the factory?
Such as it came with 245/65R17 I want to put on 245/75R17 instead.

Changing tire size can adversely affect handling, cause premature wheel bearing failure, and affect ABS and ESC systems. ABS and ESC systems (algorithms) are established for a given tire size.

I did on my van
I went from a 65 to a 75 as long as you keep the last number 17 the same. You can not go from a 17 to a 15 or a 16, etc...
One thing you would have to worry about is the tire rubbing the wheel well. To be on the safe side
You can ask a tire company.