Transmission Jumps In/Out of Gear

I have owned a 2014 Sprinter made into a 2015 Itasca Navion motorhome since Jan 2018. It currently has 45K miles and has had all scheduled maintenance performed. While traveling this year, my wife and I have noticed about a dozen times when the transmission seems to quickly slip out of gear and then back in gear. This occurs within aproximately 1/2 second. It feels like an instant momentary loss of power but the engine and rpms are fine. It seems to only occur on moderately rough roads, but not the roughest, and sometimes when there is a gap or expansion joint in the road. I have talked with a Mercedes service representative who told me he had heard nothing about this. It's hard to reproduce as the intervals are generally at least an hour apart on a trip. Has anyone else experienced this or know what could be causing it? Could it be caused by a specific vibration frequency? Any suggestions for how concerned I should be and what I should do? Thanks in advance for your input.

FrankTalk said:

I have owned a 2014 Sprinter made into a 2015 Itasca Navion motorhome since Jan 2018. It currently has 45K miles and has had all scheduled maintenance performed. While traveling this year, my wife and I have noticed about a dozen times when the transmission seems to quickly slip out of gear and then back in gear. This occurs within aproximately 1/2 second. It feels like an instant momentary loss of power but the engine and rpms are fine. It seems to only occur on moderately rough roads, but not the roughest, and sometimes when there is a gap or expansion joint in the road. I have talked with a Mercedes service representative who told me he had heard nothing about this. It's hard to reproduce as the intervals are generally at least an hour apart on a trip. Has anyone else experienced this or know what could be causing it? Could it be caused by a specific vibration frequency? Any suggestions for how concerned I should be and what I should do? Thanks in advance for your input.

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I haven't heard of a similar issue. Are you unknowingly bumping the shift lever? Intermittent issues that cannot be replicated are difficult to diagnose. About you can do is document the issue with the dealer, which you've done, and continue to monitor and document episodes.

To be precise about this your van needs so be tested with a scanner in live data and the performance plotted with particular reference to the transmission unit itself.

Your post indicates you have a possible performance issue but without substantiated test information its hard to even guess at a possible issues at play!

Its akin to asking for the Waldorfs in a Waldorf salad!
I have plenty of possibilities but on this one I am fresh out of Waldorfs .
Sorry Dennis

Curious, if Xentry has a dynamic transmission road test feature?

Not in the same way as Autologic.
With that tool in live data you have a touch screen showings all data pids.
Normally showing numerical values that will go red if they go out of spec as an alert.

You can also touch the value shown in each box and instantly it will show graph & current ramping values.

I suspect (as a hunch only) that the main pressure control valve is dropping out under temperature attack . Again with Autologic you can expand the pid and isolate a few additional vital but important values on the screen like input/ out speed and solenoid values. Then observe activity under test and their interrelationship.

Again you don't need Xentry for everything, the key is to bring the "right" tool for the job that has the feature you need to get the job done.

In fact digressing, I would say that a Picoscope not being an MB factory tool has features that far exceed the Xentry tool, BUT, and I mean BUT, you need to be able to interpret wave form patterns by oscilloscope & possible glitches with glitch capture methods. Maybe even having access to a wave form library, obtained by subscription to a workshop info system.

To reiterate its all about having enough tools in that fine English leather bound brass buggery box to diagnose it correctly.
Dennis

Thanks to all who responded to my post. I had an appointment today and Mercedes in Indianapolis. The Service Tech was unable to duplicate the problem (no surprise), no relevant faults were found and "transmission adaptations" were in spec. I was advised to monitor concern. Regarding the query by Bobnoxious, I am certain that my leg has not caused this by bumping the shift lever. It is unlike any up or down shifting I have done with the lever. I will continue to monitor. It is difficult to understand why it happens. On a trip to the Grand Canyon from Indy and back, it occurred 7-8 times the first 2 days of traveling out (~800 miles) and then not again until our return trip when it only occurred once.

lindenengineering said:

To be precise about this your van needs so be tested with a scanner in live data and the performance plotted with particular reference to the transmission unit itself.

Your post indicates you have a possible performance issue but without substantiated test information its hard to even guess at a possible issues at play!

Its akin to asking for the Waldorfs in a Waldorf salad!
I have plenty of possibilities but on this one I am fresh out of Waldorfs .
Sorry Dennis

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Intermittent Complaints like that my require extensive road-testing to be able to duplicate, and they must be able to duplicate the Complaint in order to be able to determine the Cause. Otherwise, it would be like going to the doctor and telling him that your stomach hurt a week ago, and expecting him to be able to tell you what was wrong.

In a situation like this, it might be appropriate to drop your vehicle off at the dealer and authorize them to have one of their employees use it as their personal vehicle- drive it back and forth to work, grocery shopping, errands, and even on family vacations. I had a customer years ago that had a Hummer H-1 that had an intermittent issue. I ended up driving it back and forth to work, and my wife and I used it to take another couple on several ski trips to the mountain, before we finally were able to get a handle on his intermittent Complaint.

franktalk- I have the same exact issue. 2017 passenger van 144. Ive told the dealer twice and they cant pinpoint the problem. The problem occurs while accelerating, mid acceleration their is a split second power loss and then the power kicks back in and continues accelerating. It happens at both 26 mph and 34 mph. There is no pattern and quite random. Its to the point where i dont feel confident while accelerating as i cringe when it jolts a few times a day. Quite annoying. I know its not during gear shifting but while accelearting in first- second gear? Anyone have an idea?

My experience is that it's usually low on fluid. Getting the level right on these is a pain and IMO beyond the level of attention to detail most techs are capable of. Try adding maybe 1/2 pint more, as well, once you have the level confirmed, to see if it changes the symptom. Also, if the fluid has ever been changed, consider assuming they put the wrong stuff in there and just change it yourself and start over from there. Basically, the power loss is due to the pump losing pressure for a moment, for a variety of reasons, the common denominator of which are solved by adding a small amount of fluid.

Sorry NBB, but which fluid are you talking about?

I suggest requesting the dealer review recent CV (commercial van)Tech Topics for possible additional info.

Will wait for him to respond, but I'm pretty sure he was referring to transmission fluid.

Lets be direct on this and not talk desk top/keyboard theory dicking about with half a pint of transmission fluid .

Scan tool live data on on a test will reveal what is ACTUALLY going on !
So far we we have seen two exhibiting "something similar."
Operative words here!!

In both cases the transmission had to get hot , such as climbing an extended grade and the bulk fluid temperatures were attacking the main pressure solenoids causing momentary loss of drive and that resulted in a limp mode blotting out shifting .

In both cases we replaced the valve bodies complete (exchange MB ) as this is cheaper than replacing solenoids in isolation. Repair success achieved.

Dennis

lindenengineering said:

the bulk fluid temperatures were attacking the main pressure solenoids causing monetary loss of drive and that resulted in a limp mode blotting out shifting .

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This gibberish makes zero sense.

Translated: Despite a lack of trouble codes, we hooked up our scanner, saw some funny stuff we didn't understand, then made up a bunch of non-sense to the customer convincing them to unnecessarily spend a bunch of money on a guess for a repair they didn't really need.

Oh - by the way - the fluid was low and was corrected unbeknownst to anyone when we refilled the transmission.

Step one - make sure it's plugged in - ie, check your fluid.

Yes, if it's low and it's slipping because of it, a 1/2 to full pint will be noticed with minimal risk of overfilling.

Total cost my way as a diagnostic - maybe $35 for a quart of MB fluid these days? Dennis or similar working their magic - you won't get out of there for less than a grand.

Note also there was a recent thread where someone was recommending a non-approved higher viscosity fluid based on their near zero sample of success stories - higher viscosity = higher temperature and lower fluid flow. If you aren't 100% sure the right stuff is in there, change it.

saw some funny stuff we didn't understand
Operative words indeed.
Say no more!!
Dennis

Unless you are 100% certain the correct fluid was used, I would certainly run a couple of drain and fills of the correct fluid thru the tranny post haste.

Once set-up with the proper tools (couple hundred bucks), and boned-up on Workshop instructions, piece of cake. Messure and replace what you remove with same amount, making small adjustments using proper dip stick to verify specified level.

In contrast to profit motivated professional repair shop where time is money and consumers shoulder the financial burden of unnecessarily replacing expensive components. Do-it-yourselfers enjoy the luxury of trying the least expensive remedies first.

Watch these two genuine Mercedes training videos and you will become a certified Mercedes Benz Transmission Service Specialist.

https://m.youtube.com/watch?v=n9YFglu7ZLw

Not Sprinter but same tranny.


https://m.youtube.com/watch?v=chOSihHgc4M

Bob all this sounds like a recruitment drive for armchair generals in the Middle Ages!

"YouTube" experts in those days remember were forcibly recruited on both sides to demonstrate their prowess & skill facing the foe with a halberd !

Dennis

https://www.youtube.com/watch?v=wsYpKRbRFlc

Videos are the same used at MB's Master Technician Training Academy.

Yes so was the Masters at Arms at the Butay.
Dennis