Ah, those symptoms sound familiar. Replacing the transmission and the ETC (Electronic Trans Control) is the best option for solving the problem long term. Into MY2000, the transmission was updated several times, and having the newest version is preferable. Unfortunately for those folks out of warranty, it's durned expensive.

My own dealer had some options that they talked to me about. Replacing the ETC and the Pressure Control Spring would have fulfilled the warranty requirements, but they felt the best long term solution would be just to replace the whole shebang. Fortunately for me, MB Canada covered the nearly $8KCDN bill for all that. They were within the terms of the warranty agreement to spend the $1500 or so for the other route, so I was happy that they took the more expensive route.

I understand that the V-8 version of the 722.6 had some key mods that are highly desireable.

Perhaps you might talk to some other dealers and/or indies...