My W124 CD Service Manual (pdf sheet 2702) states this procedure for my 95 E320 (722.369):

1. Drain both pan and torque converter
2. Replace filter
3. Button everything back up
4. Refill with 4 liters fluid
5. Start engine
6. Refill remaining fluid

This procedure is the same for the 89 300E. Cool, are you talking about a change in the procedure since these models came out?

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95 E320 Cabriolet, 169K