hi

to flush a auto is it possible to just take off a transmission cooler hose with the engine running and keep putting clean fluid in until it comes out clean and red and then put the hose back on and top it up till its full?

do you really have to change the filter every fluid change or can they just be patched up with new fluid till you pay someone to change the filter and fluid

Doing it the way your saying won't flush the clutch packs or the servo's, or the valve body.
It can take between 16 & 20 litres to flush the auto.
Yes, you should change the filter & gasket every service.

will the above still be ok and what happens if you dont change the filter this time but you do next time

The idea of the filter is to collect metal shavings, and clutch & band material......all of which will stuff the hydraulics.
It's like cleaning your teeth,.... but stuff it, I'll save money by not using tooth paste.......It'll come back to haunt you later.
There is a method to flushing a tranny, and it can take upto 2 hrs to do.

"next time" might become a gearbox replacement ? still sound worth while ?

The way I would do it.

1:Drop the auto pan and replace the filter AND the filter seal.
2:Clean the pan and the pan magnet.
3:Replace pan and fill with fluid.
4:Remove fans or shroud (depending on what model falcon) remove both cooler pipes and connect and drum pump with the remaining 15L in the drum to the line that goes back the box, and connect the other pipe to a hose running into a large container.
5:Have a friend sit in the car and start the engine, have him/her move the selector through each gear and let the wheels run at speed in each gear.
While he/she is doing this you need to pump in new fluid at the same rate it comming out, continue untill clean fluid starts coming out.
6: reconnect all pipes and refit fans
7:top the fluid up to the cold level or to the bottom mark and drive car untill warm.
8: top up to the full or hot mark.

If your trans is REALLY bad, you not get clean fluid with only 20L of new fluid. in this case i would do the change with the 20L and drive the car for a month and then repeat the process again with a fresh 20L of fluid and an other filter kit. and repeat and repeat untill the fluid is still clean after a month of drive.
Then whinge and complain about how the previous owner didn't look after the car properly.

when i bought my car i did a full flush and didn't change the filter. now 2 years later i changed the filter and just dumped the oil. still all sweet