I'd love to help but, I'm not a tech. I strongly recommend you wait for one of the techs to read this one. Transmissions are expensive!!! I sometimes have a little abrupt 3-4 shift and I tried to adjust it after reading a post on a similar situation. The car shifted extremely hard after!!! I took it to the dealer and told them I'm an idiot and they turned a few screws and done!!! I left the car running!!! (Mercedes-Benz of London, Ontario, Canada = friendly and honest!!!)
I'd love to hear how it comes out since I also have a 2.6
How does your car shift now?
Best of luck and be careful!!!!
190E 2.6 - 244 000 km