I had the tranny on my 93 300E 2.8 overhauled last December. I have a one year unlimited warranty on it. The 3-4 shift has been very rough on and off since then. The owner of the shop test drove it and declared it is shifting perfect and seemed offended that I have a problem (this is the same guy that flustered when I asked how much a repair he recommended would cost, saying "nobody has ever asked me how much it would cost" I guess all MB owners are made of money eh?). It only does it once in a while, and never when I back off of the accelerator (not that I ever accelerate very hard) right before the shift. When it does it the whole car shakes with a thunk. All other shifts are perfect, save for a long pause going into drive or reverse, and occasionally a hard thunk into reverse if I have been parked at an incline.
Thank you for any advice.