Repair-It

Looks like I can cure the harsh TCC apply when cold by installing a Sonnax TCC damper valve sleeve kit (68942-23K) and the solenoid itself (2402701700).

Looking at like $80 total in parts which is obviously super cheap. But it requires not only dropping the valve body (solenoid, similar labor as replacing the conductor plate) but taking it apart I believe (valve sleeve kit). This is a common issue.

Not sure I'm ready to do that but it looks like this is the necessary repair to fix the issue (as opposed to fluid changes and adaptation resets, which I haven't tried).

I will say this is probably going to be worst in cold weather so maybe it depends on just how bad it is, and how often I drive it in those conditions...

Or I could start with the solenoid since it does not require disassembly of the valve body (only removal).

https://www.fcpeuro.com/products/merced ... 2402701700

Chris williams
on Sat, Jun 27 at 01:56PM
- Torque converter lock-up fix!!!
This solenoid fixed the hard jerking on my c55 when the transmission wasn’t fully warmed up. From my understanding this issue was caused by my torque converter partially engaging/ lock-up. Now the transmission shifts smooth without needing to let the car warm up for 20 -30 min.

That is exactly the symptom. Goes away after a 20-30 min warmup.

https://www.sonnax.com/tech_resources/2 ... tification

Solenoid ID

kevm14 wrote: ↑Fri Jul 10, 2020 7:32 am But it requires not only dropping the valve body (solenoid, similar labor as replacing the conductor plate) but taking it apart I believe (valve sleeve kit). This is a common issue.

Even easier. I can just replace the TCC solenoid. Don't even need to remove all and the conductor plate. So I think the plan is, I'm just going to do the solenoid. I'll keep my new conductor plate in the box and down the road if I have an issue, OR if I want to tackle the TCC valve sleeve kit, then I will replace the conductor plate at that time, since I have to remove it. But to do the solenoid I don't even have to remove it from the valve body. Just one bolt that holds down the TCC solenoid and 2-3 solenoid, swap in the new TCC solenoid, bolt back in the retainer and bolt the valve body back to the trans.

This issue annoys me and I don't like how harsh it feels - can't be great for the engine mounts, either.

So I think I'll get this solenoid and another 5L of fluid. Hopefully that fixes it without having to also do the sleeve kit.

And I'll just reuse the pan gasket, filter and O-ring, and the adapter plug with the new O-rings. That stuff is so fresh I don't see why I can't reuse...

Ended up getting my parts early. FCP Euro is handy since they ship from Milford, CT. Even the free shipping is like 1 day, or it was this time. Crazy.

Anyway this job was easy and exactly what I had planned for. Of course I am accustomed to the trans situation so no stress this time. That was nice. Maybe 2-3 hours or something, taking my time. You could probably do this in like 45 minutes on a lift if you were in a rush but rushing transmission stuff doesn't seem like a good idea. This was the first time I've ever had a valve body out of a transmission and it wasn't difficult.

Order of operations:

Drive on ramps, jack up by diff to level or slightly higher for more room. Remove rear two bolts from center bottom cover and 4 bolts from the rear cover, remove rear cover. Drain trans fluid. Remove 6 pan bolts. Lower pan and sort of drain and just use care to avoid spilling what's left in the pan. Disconnect electrical connector, unscrew adapter sleeve, pull sleeve out of trans. Remove trans filter, set aside since I was reusing. Remove 10 bolts (same size as trans pan, T-30) and lower valve body carefully. It is heavier than I expected. May be steel instead of aluminum. Laid out some bubble wrap as a cushion and liquid barrier and then 2 layers of my blue shop towels. I brought the valve body to my bench and took those pictures.

Changing the solenoid was easy. Remove 1 bolt that holds the bottom 2 solenoids (in the picture in the last post). Simply pull the TCC solenoid out and push the new one in. Reinstall the hold down bracket and bolt. I made it tight. I tried to clean some of the trans fluid off of the valve body and conductor plate. Not sure that was really necessary but I felt like it. Used some brake clean, shop towels and air.

I did check the resistance of the old and new solenoid. They were basically identical, around 2.86 ohms. Spec is 2-4 ohms from the diagram above. But electrical health does not have anything to do with mechanical health (it is a moving part).

Installing the valve body was a little tricky. Mainly it was the weight. Once again, would have been easier on a lift. You have to align some things but mainly ensure the shift selector is centered on the pin. I knew to watch for that (didn't want a repeat of no gears, though for a different reason). Anyway I finally got two bolts started and got that going. Torqued to 8Nm....hope that was right.

Snap filter back on. Clean pan out again and reinstall that. I torqued those bolts to 8Nm also. I cleaned out the connector with electrical cleaner and compressed air.

Anyway it all went back together with no issues.

It ended up taking almost 4L by the time I topped it off hot. So I guess another 50% of the fluid has been changed. It must be at like 85% fresh fluid at this point.

As for the road test, I did not get to test it cold but I can say this: I still feel a difference in TCC lockup performance. It seems way smoother and properly integrated with the actual shifting, as they originally intended. I am actually feeling confident that I fixed the cold issue but I'll have to wait until tomorrow to confirm that. Even still, there are some notable differences in the way it drives and shifts. This is a PWM TCC clutch and, like my STS, it is intended to slip much of the time. Well, now it seems to be slipping the proper amount. This also helps drivability both because RPMs are a little higher (more torque) and because the NVH jerk has been smoothed out when applying throttle. I actually caught it hanging at 2000rpm once when I tipped in when rolling. This is because the TCC initially was slipping and then gently engaging. Again, this is as intended I am sure and feels way better.

I'll report back on the next cold start. Hopefully it's fixed or significantly reduced!

kevm14 wrote: ↑Sat Jul 11, 2020 5:31 pm I'll report back on the next cold start. Hopefully it's fixed or significantly reduced!

Yup. It's almost gone. Just the slightest bump which is totally acceptable. It is possible I should do an adaptation reset but I guess I am worried about performing the post-reset drive cycle so I don't want to reset until I am sure I can perform it per spec.

Here is the procedure:

Mercedes Transmission Optimize - Adaptation Procedure 722.6

Transmission Control Module N15/3 of transmission series 722.6 has the capability to variations in shift member clearances, filling pressures and friction characteristics in maintaining optimal functions Transmission adaptation must be performed after:

1.) Replacement of transmission assembly
2.) Replacement of Transmission Control Module N15/3
3.) If shifting characteristics seem unfavourable
4.) If shift quality has decreased after repairs or battery supply interrupted
5.) Components have been replaced in transmission General Information Concerning 722.6

Adaptation Process:
1.) Each shift and each shift member has control module requirements
2.) Adaptation values are established during shifting with extreme light loads. The transmission then functions correctly in all other driving conditions
3.) Approximately eight shifts per shift member must take place within the permissible engine torque, engine speed and transmission oil temperature allowances to effectively improve adaptation values.

a.) Up shifting using transmission selector lever is an effective method to achieve up shifts with such light engine torque

4.) Engine must continue to run for at least 10 minutes after transmission adaptation is performed. This will allow control module to record and store the new adaptation values into memory. (This is conducted in Park / Idle condition)

Note! If engine is turned off prior to the required 10 minutes time interval, all new adaptation values will NOT be stored. Transmission control module will default to previous values!

Adaptation Procedure as follows:
1.) Transmission oil temperature at 80° to 90°C optimally
2.) Connect scanner to indicate RPM and Speed
3.) Climate Control (A/C System) in OFF condition
4.) Drive on level road condition with light throttle
5.) Do NOT exceed the maximum RPM value during shift process
(1800 to 2400 RPM)

Apparently this is a clutch to clutch transmission which is about 10 years ahead of GM on that. Impressive. This came out in 1996 and GM's first clutch to clutch automatic was the 6L80 in 2006.

Anyway I am thrilled I nailed this one. Cold drivability is now what I would expect. And warm drivability is even better, too. This was a win.

First commute since fixing. The TCC locking was really noticable off a cold start going home. It is completely gone. This is amazing.

Thinking about running an adaptation reset. At mid-throttle the 1-2 cold-warm still has a bit of a bump. But it's just the 1-2 so I'm not sure if it's the torque converter clutch or the actual shift. Very hard to tell. I wish I had Star because I presume I could turn off TCC lockup and examine just the shift itself.

In (all) other situations the behavior of the lockup feels exactly as it should (as opposed to before the new solenoid which was pretty much always harsh) so that's why I think that is working fine. May just need to relearn its adaptations. Technically I was supposed to perform the reset after replacing that solenoid...

I think it's still the torque converter apply behavior. If it gets worse or continues to bother me I could look into that updated like sleeve/piston kit that LSC did on his. Still haven't done an adaptation reset either....would be nice if I could decipher in WIS whether the TCC system has any learned behavior. If not then I see no point in a reset.

Checked trans fluid level before trip. I warmed it up and used the dip stick. It was perfect. Yay.