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 30, 2020 at 12:03 am #954502 Ray ThomasParticipant The truck has 110,000 miles and the fluid has never be changed or flushed. The spin on filter has been changed twice. Kinda dirty.