The manual says every 30k for the trans I think. Look at the top of the page in the maintenance booklet, I think it will say "additional work to be performed every 30K miles".

Ps we carry the parts in the partsshop
Thanks

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Benzmac:
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM