I was told by a trained and seasoned MB mechanic friend, who ran his own independent garage for many years, that the only right way to do a rebuild on a MB transmission is with the transmission running. I would think that the replacement of parts would be one phase of the rebuild, followed by an adjustment or tuning phase with it running on a machine of some sort. The lack of such a set-up in most transmission shops is why he would never send one out to anywhere but a specialized MB shop. I wonder if this guy would agree with this?
(I just re-read the linked post: "he has had mercedes executives from germany and japan fly over just to see his homemade testing machines and he does most of the benz tranny work for large francises such as mr. transmission and aamco.". I guess he would!)

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1986 560SL
2002 Toyota Camry
1993 Lexus