So I was reading all the tranny flush writeups and was wondering why people are draining their lines/pans then filling again seperately? What I'm wondering is, cant you just empty like 12+ quarts of atf in a clean bucket, then run a hose from that bucket into the "in" tranny line, then run a hose from the "out" line into a collection pail, start your engine then watch the fluid exchange by itself? Is this not an appropriate method? Just seems like this would be waaay easier.
Snes

This may be a personal preference but with a sealed tranny I prefer to have someone with proper equipment do it. A dependable transmission shop with a guarantee/warranty is my choice over a dealer. These suckers are expensive to replace and don't require much maintenance so I think it's worth doing right.

I think I have seen them do this before and I remember a line into the dipstick hole, and a line out from the radiator with a machine that holds the fluid. That's it, and that's why I think this could be easier than it looks. Hope others will chime in with some input.

Sealed transmissions do not have a dipstick hole. With the non-sealed trans you can use a bucket and measure what came out and replace with the same amount of fresh fluid.

Pretty much how I did mine. I let it pump out and slowly poured new fluid into the return line after the cooler. I had a buddy help me and once it was pumping out nothing but clean fluid I shut it down. After hooking up the tranny cooler lines I topped off the transmission with fluid and the ran it to bring it up to temp. Temperature for proper fluid level is I believe 95-110 or so. I have it written down somewhere, but can not remember the exact number. I used a laser thermometer to check the pan temp. Knowing the fluid temp would be at least 10 degrees warmer I checked the level when the pan read 95. It is not exact, but it got me into the required range. I added a little fluid until it came out the fill port and called it good. After 2 days of driving I checked it again to be sure and all was good. That was a year ago and it has been working flawlessly.

I think I will just leave mine the way it is until someone can show some verifiable proof that you are doing any good by changing the fluid beyond peace of mind. The risks just don't outweigh the actions. What are you going to achieve by changing fluid that is proven to work the life of the device?

Not an unreasonable postion, imo. It's why I waited until 100k to do a drain and fill. If there were no change interval for towing, I'd leave it alone, but the towing interval tells me the fluid is not indestructible. I don't tow, but I do use the truck hard.

From what i have read the 90K service bulletin just says to inspect fluid, not change or flush it, the fluid is intended for the life of the vehicle