Originally Posted By: maxdustington
Did you read the post bud? He did 4 1.5 D&Fs for a total of 6 quarts to 2.8
So I was curios and did the math....
His transmission does not have 6 quarts of new fluid in it. His transmission has a capacity of 6.9 quarts. He changes 1.5 quarts at a time. He changes 21.7% of the oil each time.
First change - 1.5 quarts of new oil, 5.4 quarts of old oil, 21.7% new oil
Second change - 2.67 quarts of new oil, 4.23 quarts of old oil 38.7% new oil
Third oil change - 3.59 quarts of new oil, 3.31 quarts of old oil, 52% new oil
Fourth change - 4.32 quarts of new oil, 2.58 quarts of old oil 62% new oil
So 6 quarts of new oil was used, but only 4.32 quarts of new oil was in the transmission afterwards, and 1.68 quarts of new oil was discarded.
A drop and fill using the drain changes 81% of the oil after 3 drop and fills, and changes 43% of the oil each time.
If you are going to do a drop and fill every 30K miles, it looks like you will need to do a suck and fill every 15k miles, using your method for the same amount of fluid exchange.
So keep doing what you are doing. Change 1.5 quarts every 15K miles.
Use one of these extend a ratchets to loosen the transmission drain plug (use the 3/8 square, no socket needed). Replace the crush washer each time. They are cheap on eBay.