See attachment for the ZF factory ATF fill instructions (late model E53s with the 6 speed automatic transmission like you have). It was too big, so I shortened it for the basic, pertinent info for our BMW (as the same transmission in used in other cars like Jaguars, etc.)

Basically for a drain and refill, keep car level, drain the ATF fluid via the drain plug. Put the drain plug back in place.

Pump in ATF (original fill is ZF Lifeguard 6) until it leaks out of the fill hole. Start car and keep filling ATF until it runs out of the fill hole (you will probably use up about 4.5 quarts by now). While holding down on the brakes, shift the car manually into gears (R, 1, 2, and 3--hold it in each gear for 3 seconds), so the fluid gets a chance to recirculate in the transmission, then put the car back in park. Keep refilling the ATF until it leaks out of the drain hole again. As the car warms up, keep filling the ATF fluid as necessary (as the ATF fluid warms up, it will automatically drip out of the fill hole if you put in too much). Once the car's ATF fluid reaches 40 degrees (measure using a temp probe), you should have a slow dripping out of the fille hole (that's perfect), at this time, go ahead and put the fill hole plug back in. You're done.

Note: Facotry notes state that you should put the drain plug back in anywhere between 40 and 50 degrees Celcius. If you reach ATF temps over 50 degrees Celcius, it's too hot (expanded fluid) and you will have to let the car cool off and repeat the fill process so that the fluid slowly runs out at 40 degrees.

Total fluid needed (assuming a drain and refill) is slightly under 6 quarts from start to finish (initial fill, then the constant slow filling cycles as the car warms up).

Attached Images

6HP26-28_ZF_transmission short version.pdf (315.5 KB, 11872 views)