if your primary concern is prolonging the transfer case try this.with the engine running turn the switch to test.then after a few moments back to run.this will generate a fault code in the 4 matic computer effectively shutting down the 4 matic operation.you can confirm this with the 4matic light in the instrument console being lit.when you wish to resume 4 matic operation simply disconnect the battery for a few minutes.this will reset the 4 matic computer

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michael cole 1980 300SD gone now but not forgotten,87tdt,90 300te 4matic 95 e320 wagon