Not a good idea to have the transmission flushed on any older transmission…unless u bought the vehicle new and have it done at every recommended maintenance schedule in the owners manual, having it flushed could actually cause it to completely malfunction and need rebuilt ….however, I’ve made it common practice to change the transmission filter and gasket and fresh fluid when I buy a vehicle…my trailblazer was a bit sluggish and shifted hard when I first got it..the previous owners never changed the oil it seemed or did any maintaining in it…it helped a lot…
also, with this engine and vvt set up, the owners manual even states to use full synthetic 5w/30 oil …u will want to keep it changed and clean as possible cuz it will damage the screens in the vvt and u will lose power that way as well…they’re very fine screens that oil is pushed through to engage the second cam to get the speed andhorse power…that’s how they get both hp and higher torque out of these suvs…kind of interesting really …one of the two things I love about my trailblazer that’s kept me from junking it lol…the other thing being the turning radius…compare the front steering knuckle of a trailblazer to any other type of pickup or suv…it’s really interesting to see ….