1. Remove and discard automatic transmission.

2. Install manual transmission, generally sourced from a manual 240D.

I did this and it solved all my transmission issues in my 300D.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.