I do this. I've decided to change the gasket and filter somewhat less frequently and change the fluid more frequently. When I extract the fluid using a topsider, I get out between 2.0 and 2.3 quarts. So what I do is do it several times over the course of several hundred miles. If you do the math, doing this four times gives you ATF that's about as pure as it would be if you drained the pan and the torque converter....and you've used just a little more ATF than you would with the conventional method.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 161k miles
06 E320 CDI "Rutherford", Black on Tan, 180k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 147k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 81k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife