In a recent surfing session, I came across some chaps in the states who have come up with a way for DIYers to flush all the transmission fluid from the gearbox without the need for special machinery.
What they do is this.

1) Drain the fluid from the reservoir, remove and clean the filter. Replace the filter and refill with new oil.

2) Disconnect the return pipe from the oil cooler, and place the open end in a bucket containing new oil.

3) Attach a temporary pipe to the oil cooler and place the open end in an empty bucket.

4) Start the engine and allow the gearbox to start pumping the fluid. The old fluid collects in the empty bucket, whilst the new oil is drawn into the gearbox from the other bucket.

5) Whilst this process is on-going, regular checks are needed to ensure that, the collection bucket doesn’t overflow, and the reservoir bucket doesn’t suck dry. The dipstick also needs regular checking to ensure the correct oil level is maintained throughout, as topping up may be required via the dipstick tube.

6) When the old darker oil in the collection bucket starts to change to lighter red, the whole system will contain new oil.

7) Re connect the return pipe to the oil cooler, final check on the dipstick, refilling as required, and hey presto 100% oil change.

- (#7619) dave Bright, 12 Mar 03