Hey, was just at the tranmission shop and asked the guy how long the tranny should go for on my 2003 GMC SIERRA truck. He said 60, to 90,000 miles, if you dont get it flushed. He said if you change it every 30,000 miles, from what he has seen it will just keep going and going. If towing every 20,000. So your thinking... "is he right?" Well my brother hadnt done his on his 2002 Sierra for just about 90,000 miles and guess what went. Not even 3 days after I told him this! Pass it along.