Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › transmission filter/flush 2011 gmc 2500hd › Reply To: transmission filter/flush 2011 gmc 2500hd April 29, 2020 at 10:31 pm #954497 Richard KirshyParticipant Mileage??? Has the transmission ever been completely flushed before? If not may not be the best thing to do.