There is no central diff in W124 4matic, only clutches. What you are thinking is at best not possible, worst idiotic. Just fix the system they are very easy to work on.

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600SEL '91
300E 4Matic '88
240D '83
280SE '77
350SE '73
The most complex systems can fail in the simplest way.
Contra verbosus noli contendere verbis, sermo datur cunctis, animi sapientia paucis.

i don't believe in the lord! He's never bought me a Mercedes Benz.