I've been wrestling with the 2-3 flaring for over a year on my 300E. According to Gilly, there is a little known repair kit for this problem known as a K1 accumulator kit. It costs all of $2.71 from MB. I don't know the part number for your trans, but the one for mine was 126-270-44-77. Esentially, its a spring kit. I haven't put it in yet (waiting for the Rover to get out of the repair shop). For less than three dollars, its worth a try. There is also some literature out there that points to the B2 reaction valve. Do a search on trans flaring and you may come across it.
'86 Alfa Romeo Spider
'84 Harley Davidson FLH"X"
'70 FJ40 Land Cruiser (basket case)