I have stop. And i wil take some day of break and then i wil study :

http://www.tglmarketinginc.com/mbforum/servman/MB%20Service%20Manuals/www.pauldrayton.com/uploadfiles/merc/Service/W123/w123CD2/Program/Engine/615/05-412.pdf

It is about 05-412 intermediate gear (hint from Vox incognita).