CL500 722.6 TC not locking up

[E240estate]

As title really, car drives absolutely fine and no codes.
But it's obvious the torque converter does not lock up as it's very revvy on the accelerator.
Most of the time it shows OPEN it will go to SLIPPING.
So even on the motorway it never shows much more that about 45/255 locked.
There's always a rev difference of at least 20.
Is it a reasonable next step to change the TC solenoid? Pretty confident at doing this as part of a diy fluid and electrical connection change which is due.
Or do I need to test it some more to be sure this is the trouble?

 

[Dodipops]

You should be able to lock the torque converter using diagnostics, think it only stays locked at low speeds for testing but that would prove it does lock??

 

[BlackC55]

If its not locking (via diag computer) I would fit a re-furbished torque converter and get the valve body overhauled.

 

[Petrol Pete]

Owning and driving a 18 year old 150K mile C55 AMG can sometimes bring out a bit of paranoia , every new click or rumble requires investigating.

Long story short I thought I had lock up clutch slip . I plugged in my trusty DIY iCarsoft MB2 which indeed showed crank and transmission were not spinning at the same speed with the clutch in. Slight Panic

My trusted mechanic basically said the iCarsoft is not quick enough to read what was going on and it would need an oscilloscope or a much more sophisticated scan tool to be certain.

After a test drive he sent me on my way and told me not to bother him unless it was serious next time .

That was many months and a few thousand miles ago , so far so normal.
:
I understand that when the lock up clutch is in the crank speed and input shaft of the transmission 'are as one' , Is my bloke right in saying 'proper' scan tools will show this. ?

 

[mersum1es]

in my experience 722.6 is rarely fully locked.

 

[E240estate]

Incredibly helpful diagram, acoording to which I did not go outside of A and B in my testing, also interesting comment about the icarsoft mb2 which I was using also, It's obviously not a dealer level piece of kit so quite feasible it's not giving 100%