Just to add a little bit to all this. I've been using a disposable AC Delco trans filter that I installed inline to the trans lines near the front of the truck. Just an extra thing to catch any small debris I guess.
Also, did you ever have your trans fluid flushed? The ATF in the pan is only about 1/3 of what is in the system. So replacing what's in the pan isn't good enough. I've taken to doing a flush every two years (because I tow), and have had no problems at all with the trans.
I've written this a number of times in greater detail, but it is possible to do a flush yourself. Buy 15litres of Valvoline Dex/Merc ATF. Drain and re-fill the trans pan. Then disconnect the trans cooler lines at the front of the truck. Put the outlet one into a big pail (both if you don't know which is which). You'll need an assistant. Start the truck, and run it until about 2litres comes out. Shut it off quickly. Top up the trans with 2litres. Start the engine again, and again let 2litres come out. Shift the trans into a different gear (with foot on brake obviously!) each time you repeat this. Keep repeating until clean ATF starts going into the bucket. Its handy to have a few buckets so you can tell. It takes about 15 litres in my experience. This is because you're replacing all the dirty ATF from the transmission passages, torque converter, ATF cooler, lines, etc. I think the totally system capacity is around 12-15 liters or so. It's handy to have some extra hose around. Ideally the ATF should pass through the trans cooler (in bottom of rad) before it comes out into a bucket - this way you're flushing the trans cooler too.
What was the color of your ATF out of curiosity?