85 280SL euro transmission hard shifting.

[desert]

My 1985 280SL Euro, 55k on it with auto trans is starting to shift up hard between gears, it's always made you aware that it was shifting but now it can snap you back going from each gear. It does it more when it's cold although right now it's way over 100 degrees here in Arizona but sometimes it still does it when it's really warmed up. First, any ideas why it's shifting so hard ( oil level is fine and oil is clean) and second can you tell me the model number of this transmission that is married to the streight six engine in the 85 Euro 280 SL. Thanks for any advise. Desert