a flush is a high pressure process that can blow out seals inside the trans in areas that don't typically see high pressures.
It also typically introduces a bunch of foreign contaminants from the trans flushing system... such as metal filings from a previous transmission flush.
Drain, new filter, wipe off any metal filings that have been collected on the plug's magnet ... if there is a pan removal as well you can wipe that off as well, put it back together and refill and done.
If you feel like you didn't swap enough fluids you could always do it again after a few miles but I don't know anyone that would.
It also typically introduces a bunch of foreign contaminants from the trans flushing system... such as metal filings from a previous transmission flush.
Drain, new filter, wipe off any metal filings that have been collected on the plug's magnet ... if there is a pan removal as well you can wipe that off as well, put it back together and refill and done.
If you feel like you didn't swap enough fluids you could always do it again after a few miles but I don't know anyone that would.
