A couple of month back I had my transfer case rebuilt for a failed bearing. They did a transmission service including the torqueconverter. The transmission is no longer shifting seamlessly particularly 4th to 5th. I had the car at the dealer yesterday and they confirmed my observations. Ran the diagnostics and came back with no faults and all of the adaptations within spec. They did run an update to the software and the 4th to 5th upshift is still noticeable. They recommended a transmission service, but obviously since I just had it done I am doubtful that that alone will cure this. I have in the past come across this video and wondering (hopeful) that this might fix the issue.

The other possibilities are the torque-converter lock-up is going south (I notice rpm fluctuations when I apply the gas on the highway which I'm not sure I did before) or the transmission it self is going belly-up. My indy that did the transfer case repair said that it is relatively simple to diagnose the TC lock-up by disabling it with the DAS.

​​​​​​Any insight would be greatly appreciated.

TIA

My experience is with GM/Ford/Honda transmissions so you may want to toss my observations .....

You mentioned a failed bearing and related transmission service so I assume transfer case shares the same fluid as transmission? If so, it may be possible there is debris trapped within the transmission that is affecting solenoid operation.

I've seen valve body contamination from failed transmission components. It can't be removed by just fluid/filter change as the debris gets trapped within check passages and solenoid screens. Some types of transmission coolers (thermostat controlled) can't be flushed after failure and in many cases repairs aren't warranted unless the converter is replaced.

I would think that MB specific diagnostics could help pinpoint specific failures to verify. At any rate, a valve body service could be a reasonable initial approach before pulling the entire transmission. But again, I would first look for diagnostics to help point to specific component operation.

Hopefully more knowledgeable MB techs can add to or correct this info.

Thanks for the feedback. Yes this was my line of thinking as well hence the link to a video of the procedure to do the cleaning. They did run the computer diagnostics and software update and came up with nothing.

An additional update. I called the tech who drove my car and he tended to eliminate the torque-converter based on his driving experience. What he did suggest is having the transmission fluid tested for coolant contamination. So I think that will be the next step.

I know people were complaining about the W211 chassis having coolant contamination issues due to a poorly engineered radiator, but I haven't heard of this issue being present on the W212. Also, I think that if it was a coolant contamination issue you'd be experiencing improper shifting behavior throughout all the gears.
Coincidentally mine does something similar on upshifts, usually between 40 to 50 mph. I haven't played with the valve body or shift solenoids, but as soon as I get my own garage and a lift I'll poke around in there. If it's not a shift solenoid or TC, the next culprit could be the clutch pack for the specific gears, in our case K2/K3 if I remember correctly. That would require a tranny rebuild.
A very unlikely scenario would be the presence of buildup in the valve body fluid channels, but that can be checked for when cleaning the shift solenoids.
One non invasive test you could perform is taking out 100ml of tranny fluid and sending it to Blackstone, they can check for both coolant contamination and clutch material debris + other stuff to give you a better image of what's going on in there.

This reminds me that Oda112 did a pretty extensive past posting about the valve body, maybe look it up for additional info.
+1 on Blackstone, I do a once/yearly oil analysis on each of our vehicles.

First of thanks for the reply and interest. So I took it back to the indy that did the transfer case repair today and they drove it and didn't find anything wrong with the way it drove and scanned it for faults (none) and looked at the adaptations and said they were normal. The owner also provided a lengthy explanation as to why he didn't think that any bearing debris would have found its way back to the valve body. Part of the explanation being that it would have to have gone past the filter. The night before I called an outfit in California that rebuilds the valve bodies and he basically said the same thing ie that it was unlikely due to contamination. He suggested that the adaptations needed to be adjusted.

Now I should add that during normal or harder acceleration it really isn't that noticeable but I tend to be very light on the throttle and there is a definite pause in the 4th to 5th shift. It feels like the system wants to shift and the ECU cuts back fuel during the shift so I kind of decel for a bit then it shift and it pushes as opposed to the 5th to 6th shift which is utterly seamless you can't feel it at all.

I will do as you suggest and pull a sample after it has warmed up but not sure the best way to go about it because of the overflow tube its not like I can come in from the side and extract some fluid would need some kind of hook tube to suck it out.

Oda112 - Could you point me to the posting referred to above. I did do a search on your posts and found a couple that related to the valve body but not sure if they are the one being referred to above. Also reading your posts I was relieved by your comments that you shouldn't feel the shifts because it my recollection that that was one of the things I really liked about this car was you had no idea when it was shifting.

https://mbworld.org/forums/e-class-w...ml#post7319529
It might be this one, it will give you a better look at the inside workings of your tranny. I have a PDF describing how the shifting actually occurs, I'll put it here.

So one of your posts you talked about a tranny rebuild based on some Youtube videos I have looked at it doesn't look like that huge of a deal. What do you think?

For some reason I can't open the .rar files. Something about the archive being damaged. (I feel like I am at work)

Did you ever find the cause of this issue, i have 6 years with my car doing the same, the dealer says that is normal, this is because the car is meant to be driven in highways mostly.

No a year later it is still the same. So I guess that it isn't an impending catastrophic issue. My plan is to continue to drive it until it needs the fluid changed again and drop the TCU and clean it then.