CLK 270 cdi & it's autobox

thebiglad

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Aug 23, 2018
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'05 CLK270 cdi
Hi all, recently in France the speed limit on N or D single carriageway roads has been reduced to 80 kph (50 mph).

This leads me to pose the following question : at what speeds does the torque converter 'lock-up' and does it only lock up in top - 5th - gear, or does it also lock up in 4th, 3rd etc and at what speeds.

I'm not sure the TC lock-up is working fully or correctly in my car, particularly during the long warm-up time.

So it seems like I often do not achieve lock-up due to either temperature and/or roadspeed.

Can anyone shed light on this topic please ???

Cheers
Dave
 

PobodY

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CLK350 Sport
The 7G-tronic (fitted in facelift models) will lock in every gear.

According to Wikipedia the 5G-tronic (which I assume was in the earlier models) will lock in 3, 4, and 5... but that might be application dependant (so maybe only the AMG models?).
 
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thebiglad

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Central France
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'05 CLK270 cdi
Thanks for the reply PobodY, Mine is the 5 forward speed box so I'm guessing it's the 5G-tronic unit.

So, assuming it is supposed to lock-up in the 3rd, 4th and 5th, it would be great to know at what road speeds or conditions it should lock up ???

A separate thought just crossed my mind, I would if it would be a good idea to reset the adaptation function on the 'box, to establish a baseline to move forward ???
 

PobodY

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Could part of the problem be that it's holding the gears longer (to give higher engine revs) to help warm the engine up? - I know my 7G-tronic behaves a little strangely until it's warmed-up, then everything goes back to normal.
 

whitenemesis

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Lexus RC300h F-Sport 2019
From WIS
The characteristic curves shown in the diagram illustrate the
different operating states of the torque converter lockup clutch in
relation to the accelerator pedal position and the transmission
output speed, plotted for one transmission gear.
upload_2018-12-8_15-20-12.png
Operating characteristics of the torque converter lockup clutch
A Open
B Slipping
C Closed
d Accelerator pedal position
n Transmission output speed

Variables influencing the states of the torque converter lockup clutch
  • Accelerator pedal movement
  • Uphill and downhill gradients
  • Transmission shift functions
  • ATF temperature
  • Durability requirements
  • Load condition
  • Engine control influences
 
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thebiglad

Active Member
Joined
Aug 23, 2018
Messages
316
Location
Central France
Car
'05 CLK270 cdi
Hi WN and thank you for the above info.
Could part of the problem be that it's holding the gears longer (to give higher engine revs) to help warm the engine up? - I know my 7G-tronic behaves a little strangely until it's warmed-up, then everything goes back to normal.
Hi mate, during warm-up she seems to behave normally except for torque lock-up. Unfortunately the problem seems to be that the box - even on light throttle - only goes into 5th gear at about 85kph and TC lock-up at about 90kph. So for most of my A-road stuff (where the legal limit is 80 kph) the 'box hasn't locked up ??? It's only when I'm tramping at on at perhaps 100+ that the lock-up is felt to happen. Great for motorways, not so go for local work.

I think I'll try a reboot of the 'box adaptions and then an oil and filter change and see where we go from there.
 

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