The change on 2nd to 3rd in my 1987 300SL is sluggish especially when the car is cold. The change up doesn't happen 'til quite high revs, even when the engine is not heavily loaded, and when the change does happen there is a gap between gears when the engine revs before finding 3rd. 3rd to 4th is fine. Fluid levels seem fine. There is also a slight whine from the trans when in second. Don't know if this is related to the shift problem.