Nice, that is also how ford 3/4-1 ton truck guys with zf5 cure their getrag rattle: fill with one extra quart of atf through the shifter hole.
On my former 190Dt with 717.411, I drained the fluid(which must've been some high end synthetic like redline Mtl or 75w90ns as the shifting was great even cold) and refilled with normal dex 3 and my idle rattle was worse, even when cold. My former fluid didn't let it rattle noticeably until it was stinking hot...
Then again I only filled it up to the fill plug as it was installed in the car

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97 e300d, 78 300Dt, 95 E300d, 94 E320 estate