Just got this diagnosis from the dealer while the S550 was in for a lack of power/no down-shift when accelerating at highway speeds.
Code 2783 (Friction power of torque converter lockup clutch is too high) LI27.20-P-055758
Their repair cost is a paltry $4273.02

I'd love to have you guys weigh in on what I should do. There are some trusted indies in the area that can do the work, so at a minimum that's what I'll do.

Thanks!

 

merc 7g box is a horrible thing, its not reliable, and on a UK forum a very well known Merc indy who is a bit of a box specialist says he's been very busy in the last 6 months with many of them suddenly dying.

that said merc's TC lock up clutch in all models makes the 7g box look really good !!

 

Well, it turns out it's all covered under my extended warranty that just paid for itself.