Transmission shudder from 3rd to 4th- '94 E420

[JerryS]

Please help.....I need some sound advice. I have a 114K miles 1994 E420. A few weeks ago I reversed the car fast for about 200 feet, and when I shifted to forward the car shook severely. I limped home, and the shaking lessened as I drove. The car shifted between all gears, but the shifts seemed hard. When I shifted to reverse, the transmission made a grinding sound when moving backwards.

I took the car to an independent shop, and they said I needed a rebuild, which I had no option but to have them do. They said that there was a known weakness in the transmissions of the E420, and going fast in reverse caused a piston inside the transmission to break and mess up the transmission.

When I picked up the car a few days ago after the repair, it shifted fine from first to second to third, but shuddered between third and fourth. The shuddering was about four or five quick grabs before the fourth gear took hold. This was noticeable under acceleration or when going up a hill. I took it back to the shop, and they made some adjustments, but the car still shuddered between third and fourth. I took it back again, but when I went to pick it up this afternoon and drove it, it was shifting sloppily between all gears and still shuddered between third and fourth. Now they are trying to tell me this is normal and that there is nothing wrong with the transmission rebuild. There was no shudder like this before the transmission was damaged, so I can't believe it is normal.

My question is: did they do a bad job on the rebuild? Is there some other problem that could be causing this? What should I do next? Any advise would be greatly appreciated.