There is a way you can "flush" the tranny yourself. At the dealer they will tell you to do a drain and fill, but that really only gets about 1/3 of the fluid clean. It doesn't get any of the fluid out of the torque convertor, lines, cooler, etc. What you do is pull the drain plug on the tranny, then get someone to crank it up. While they are in the drivers seat, have them change the shifter from park to reverse to drive about every 5 seconds. Meanwhile, you will slowly be adding fluid from the top. Keep an eye on the fluid draining out to be sure you are adding the adequate amount. When I do flushes at work, I use about 15 quarts and that always gets it clean. It won't be cheap buying 15 qts. of MaticJ fluid, but its A LOT cheaper than paying them to do it. Anyway, back on subject. Continue adding until you've done about 10 qts. Then shut the truck off and let it drain the rest of the way. From there, plug it up and add a few quarts. I don't remember right off how many it holds, but start with about 3, then check the level w/ it running. You may have to adjust the level from there a little.