I want to do a transmission flush on my Trailblazer but I'm afraid with really no knowledge of the maintenance history and the fact that I have 145K miles on it, Would doing a flush actually hurt my transmission like cause slippage? The last time I check the trans. fluid was like at an in between color, not bright red but not totally black more like reddish brown. I just thought I'd throw it out there to check with you guys who know way more about our vehicles than I do.