The 4-matic part(s) consist of transfer case, locking rear differential, & the front differential. The transfer case is a bolt-on that has it's own drain & fill plugs. It does use ATF.
OF course there is a computer & hydraulic componets as well.
The trans modulator has a rubber cap that can be removed & then the key underneath can be pulled slightly out & turned counter-clockwise to soften the shift.
MERCEDES Benz Master Guild Technician (6 TIMES)
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44 years foreign automotive repair
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190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)