Regarding the flush....
I really think this is an internet wives tale. I own a "flush" machine and I can tell you that there is no way that particulates are getting disturbed or "flushed" by using this machine.
Really, think of it as a fluid exchanger not a flusher to get a more accurate perspective as to what it does. Using this method is much preferred to the "drain and fill" because it will extract all the dirty fluid from the torque converter as well.
However, it is important to make sure that the shop is not dumping your Lifegaurd fluid on top of another type of fluid in the machine. This type of contamination is a no-no. When I do mine I will flush it at 50K and change filter at 100K
Funny though my own research has the same results as you guys.....still trying to decide if lifegaurd 6 or lifegaurd 8 is the correct fluid. According to the ZF website lifegaurd 6 is listed as the correct fluid for 6 speed transmissions, but I am hearing lifegaurd.
Again flushing is only bad if the shop allows different kinds of fluids to mix in the machine. Other than that fine to do.
Mike
ASE Master Tech/ L1
Bookmarks