722.6 transmission slip

[amazighman]

Hi fellas.

I have this old 2004 W211 with 722.6 transmission.

The issue is it has a slight slip when going from 1st to 2nd , worse when cold ,less noticeable when warm.

Basically as you pull away the RPMs go up as they should till 1800 then they drop suddenly to 1600 with a slight jerk , then pick up again and then gear change happens into 2nd .

Changed fluid few times ,its red and clean..
Changed valve body with good 2nd hand
Changed transmission filter.
Pan was clean no metal shavings or sludge
Fluid level is spot on.
No faults on diagnostic

I ran out of ideas

 

[Dodipops]

You could try readapting the shift points?

You could maybe lock the torque converter with the diag see if that stops the fault?

What sort of miles is it on?
Could just be clutch pack wear?

 

[amazighman]

You could try readapting the shift points?

You could maybe lock the torque converter with the diag see if that stops the fault?

What sort of miles is it on?
Could just be clutch pack wear?

Its 180k

Clutch pack wear maybe , but pretty much goes away when warm.

 

[amazighman]

I only have Icarsoft , doubt it can lock anything

 

[Dodipops]

Goes away when warm because the clutches expand, when setting these up you get shims to adjust the play in the pack and we are talking fractions of mm difference. That can make the difference between slipping and not

 

[amazighman]

Goes away when warm because the clutches expand, when setting these up you get shims to adjust the play in the pack and we are talking fractions of mm difference. That can make the difference between slipping and not

To be honest I dont know.

The blip in Rpm happens way before the new gear engages , somewhere in middle , me think maybe pressure is lost somewhere

 

[Petrol Pete]

Sounds like the clutches are worn. One option is to add one of the many liquid 'snake oil' products out there that are a supposed 'fix' this . Never had to do it myself , but might be a last chance alternative before having the box re built . All the best with it

Here is an insight into the clutches.

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[BlackC55]

The gearbox will need to be stripped to see the issue. No amount of fluid changes or a valve body replacement will fix this.

 

[Petrol Pete]

^^^^ What he said ^^^^

 

[amazighman]

Could well be the case.
If i drive it in Sport mode obviously starts 1st gear then struggles to engage second under light throttle.
However if I accelerate harder then the problem doesn't happen.
In comfort mode starts on second gear absolutely silky smooth no issues

 

[amazighman]

Found an old thread exactly.same symptoms as my transmission. This is from 2010 so a while ago

W211 gearbox kick / fake gearchange

Hi guys and gals, Since buying my car, I have pretty much been exclusively driving in "C" mode. When starting to use "S" mode I noticed what may be a problem? In "S" when accellerating gently from a standstill, the engine revs to about 2000rpm, then you feel a kick and the revs drop...

forums.mercedesclub.org.uk

 

[Jobsworth]

It sounds like the torque converter lock up clutch to me. It’s controlled by a PWM signal to the solenoid, but they do get bumpy with age. Changing the solenoid may be a good first step. It’s not massively expensive

 

[amazighman]

It sounds like the torque converter lock up clutch to me. It’s controlled by a PWM signal to the solenoid, but they do get bumpy with age. Changing the solenoid may be a good first step. It’s not massively expensive

I changed the whole valve body with a second hand one.
Would a lock up clutch affect only one particular gear?

 

[Dodipops]

It doesn’t affect all gears no, it’s designed to allow a certain amount of slip, especially in lower gears at low revs, floor it and it allows less slip. That’s why you need to have it locked via the diagnostic to prove the fault goes away.

Using a suitable diagnostic you can also get lots of info on the clutches K1 K2 and K3 that during a slip condition will be noticeable in the data.

 

[amazighman]

It doesn’t affect all gears no, it’s designed to allow a certain amount of slip, especially in lower gears at low revs, floor it and it allows less slip. That’s why you need to have it locked via the diagnostic to prove the fault goes away.

Using a suitable diagnostic you can also get lots of info on the clutches K1 K2 and K3 that during a slip condition will be noticeable in the data.

Lockup clutch is part of the torque converter right?
I can understand that my torque converter is on its way out

 

[Dodipops]

Yeah when we say lock up clutch that means locking the torque converter so no slip from that, it’ll give direct drive to the clutches and if the symptoms disappear you’ve found your fault, if not then the slip is happening in the clutches themselves.

 

[amazighman]

Yeah when we say lock up clutch that means locking the torque converter so no slip from that, it’ll give direct drive to the clutches and if the symptoms disappear you’ve found your fault, if not then the slip is happening in the clutches themselves.

Need star for that...
Doubt it can be done using Icarsoft V2.0

 

[Dodipops]

Not sure I’ve never used it.
I have autel maxis and it has the function.