Hi there,
Go to the main Shop Forum menu, then select the SL forum. At the top of the page there is an advertisement for the digital servo upgrade. (Unwired tools logo). Click on it! You can get the latest version of the unwired tools digital upgrade servo from them for $699, or from Performance Products, or from Phil on this website. Your Mechanic has a $100 profit built in to his price!
It is about a 2 hr job to convert to the digital servo. You can download the instructions from the unwired tools website to see if you feel up to the task.

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C