One thing that can play a role in transmission performance is making sure the transmission filter is not clogged. The best way to do that is to drain the transmission (and torque converter too), lower the transmission pan and unscrew the old filter and install a fresh new one. Then install a proper quantity of quality transmission fluid. This is something you can do yourself IF you have some mechanical skill and the where-with-all to jack the car up and install floor stands and get under the car to do the work. You'd be surprised how a transmission filter can clog with transmssion debris over the miles and years. If your filter was clogged and you replaced it, you may well have a sweeter performing tranny. Do this BEFORE consulting a "professional". You may save lots of money.

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Jim Sehl
'80 350SL
'80 300TD
'84 190D
'86 300E
'92 600SEL
'94 S420