Transmission flush
I worked for and ran a quick lube for over 5 years in my past. We a had machine called a T-Tech. It was a device for replacing all the fluid in a trans by means of the trans cooling lines. It wasn't pressurized, if you will. The fluid came out as fast as the car pumped it through, and the machine replaced it with very little power. I really don't think the problems lies within the process, but more so with the reaction of the car to entirely new fluid. If you have underlying issues, or wait till 150K for your first service you're far better off just leaving alone completely. However, this was about 10 years ago and I know fluids have come a long way. I only had one problem once and that was a Ford Aerostar that had trans issues to begin with. The customer thought a flush, and plan/filter service would make it better. I declined to help him knowing it would make it worse but he pushed...long story short a tow truck brought his van home that day. IMHO, if you are going to change your fluid then do it, and do it often as the old stuff will never get too dirty to be different than the new stuff. OR just leave it alone all together. The complete fluid replacement is a great idea and works well, but if your fluid is trashed and your transmission is used to that old sticky fluid that might be keeping things together, replacing all that old stuff may contribute to transmission failure. Like I said, I'm not expert, just my 2 cents. Hope this helps....