I need to change the trans fluid in the superduty soon. Being that it is an older transimssion, and I have no idea when the last time the fluid was changed, should I just dump the pan, change the filter and re-fill? Or, have it completely flushed? I have heard that flushing an older transmission will likely cause more problems, and be the demise of the transmission, because it knocks loose any crude that is lurking in the transmission and usually stuffs it in something important.

What are your thoughts?

Personnally I would drop the pan and change the filter. It also alows you to inspect and see if there is any unwanted chunkies in the pan. Depending on the year, your torque converter may or may not have a drain in it. If it doesn't just fill the pan and run it for a while and drain/fill again. I don't believe flushing a tranny will hurt a thing, if anything it helps. If doing a trans flush causes the trans to die it didn't have long left anyway.