Hey All, I bought my 2001 Yukon originally at 108k miles back in 2010. I currently only have 140k on it, as the first half of ownership was finishing college and grad school and I haven't had to drive much since then either. I started doing my own work on my vehicles in the past 3 years using the Yukon to learn on, and I've come to realize that I have no idea if the transmission fluid was changed out at 100k from the previous owner. I really don't know anything about the maintenance that he did (I bought the truck on Craiglist private party). From looking on this forum and on some others, I have seen the recommendation NOT to change the transmission fluid if you are way past 100k miles and haven't had any problems. I don't fully understand why, though I think I read something about different seals. The transmission fluid is definitely brown, though not as brown as I would think it would be having gone through 19 years and 140k miles if it wasn't changed at 100k. So my question is, do I go ahead and change it under the assumption that it wasn't changed at 100k? Or is there some risk to changing it now that it is so far past the time and I should just ride it out? I've read of dropping the pan and replacing the filter, not flushing, so that's what I was thinking of doing. Any help is appreciated.