POWER flush is bad, using the transmission itself for the flush is fine.
IF you have a transmission that is STILL using bands, maybe. Lots of car manufacturers
went with the muliplate brake method after Chrysler invented the Ultradrive, it was the
first automatic to have no bands or sprags, people followed suit. Be it a band or multiplate,
it's called a brake.
Basically, the band is a steel strap with friction material bonded to the inside surface. One end
of the band is anchored against the transmission case while the other end is connected to a servo.
At the appropriate time hydraulic oil is sent to the servo under pressure to tighten the band around
the drum to stop the drum from turning. Way way back, you used to be able to tighten the bands.
The multiplate brake is constructed in a similar manner to the multiplate clutch. It locks or holds a
rotating component of the planetary gear set to the case of the transmission. Hydraulic pressure
actuates the piston and return springs return the piston to the rest position in the clutch drum
when pressure is released. Friction discs are steel plates to which friction material is bonded. They
are always located between two steel plates. The friction disc inner diameter is slotted to fit over
the splines of the clutch hub, similar to the multiplate clutch; however, the steel plates spline to the
transmission case, thus providing an anchor. The band locks the whole planetary gear set by the shell.
There are two types of bands. Static, and Dynamic. Dynamic is like a sponge, the material holds
oil, but when applied the oil is squeezed out so the drum stops. Static is a harder material with
a high sheer strength and just grabs the drum.
One major rule is, if the transmission is a SEALED unit, never flush it. If you have no Dipstick,
plus no service interval listed in your manual, then you never service it. They're all using 100%
synthetic, and will last the lifetime of the car. The lifetime is conjecture too, when the trans
fails, that was the lifetime of it... The mercedes NAG1 is a lifetime transmission, you never have
to change the fluid or filter, but YOU CAN, and I have...
The danger is the POWER FLUSH, them pressuring fluid through it, NEVER do that. IF you want
to flush, use the transmissions own pumps and cooling lines, never pressure it through. The
power flush is done the opposite of fluid flow, this will dislodge anything trapped in the system,
because it goes the other direction. That can trap those dislodged particles in the torque
converter, and there lies the main problem. So, using the transmission itself, flushing in the direction of
flow is perfectly safe. The "crap" stays in the system, the new fluid flows over it... There are
two ways to flush this way, you can look it up.