Rumble Strip Noise- Cured

Here at the Global Sprinter Research Center, I am happy to announce a cure for
Rumble Strip noise. Longer term 'Clinical trials' are now in progress and
looking promising.

Backround info- I was finally able to direct significant time and effort to
researching RSN when the PERFECT patient arrived in the form of a client 2005,
140" 2500 cargo with approx 62,000 miles.

This particular Sprinter had a history of recurrent limp home mode with codes
related to sporadic MAF sensor plausibility issues. The vehicle NEVER misbehaved
when visiting various dealers. My new client asked me to help diagnose the LHM
problem and to keep and use the vehicle indefinitely, until cured.

I did cure the vehicle of its LHM issues, and as luck would have it, this
particular Sprinter was coincidentally cursed with moderately severe, and more
importantly, predictable and easily repeatable RSN.

Since I was able to utilizing this Sprinter as my daily driver/shop truck and
was monitoring ECM sensor data for the LHM issue, I included additional TCM
instrumentation in the name of RSN research.

The findings- Several years ago (on a thread in the Yahoo Sprintervan
group) I identified the source of Rumble Strip Noise to be the TCC (torque
converter clutch). I had theorized that the TCC solenoid's modulation was
responsible for the torsional vibrations and then magnified by the Sprinters
vast body panels.

Using my research 'volunteer', I measured the TCC solenoid's duty cycle control
frequency at xxxHz. Remember, the TCC is NEVER fully locked, but operates in a
duty cycled slippage range of between 5-95%.

Mbenz's use of 'controlled' TCC slippage was intended to allow controlled
bypass of fluid to the transmission cooler so as to reduce temp of both the
fluid and the torque converter and IRONICALLY to dampen engine torsional
vibrations. I put the word 'ironic' in capital letters because under certain
conditions, the opposite appears to occur.

NAG1 variants are employed in numerous Chrysler vehicles and according to
factory tech literature, in most all of these vehicles, TCC activation (slippage
mode) is used ONLY in 3rd, 4th and fifth speeds. My data showed that the diesel
Sprinter engages TCC activation in ALL 5 forward speeds.

My instrumentation also clearly allowed me to observe the 2 operating phases of
the TCC- The 'ON' phase where engagement induces controlled slippage of between
5-95% and the 'OFF' phase where no TCC action takes place (100% slippage of the
TCC-in other words, deactivation).

I have concluded that RSN is not only the result of solenoid duty cycle
modulation but even more importantly, overly aggressive activation software maps
whereby TCC control is switched 'ON' at VERY low speeds and very light loads
(both accel and decel) resulting in the engine's torsional vibrations being
transmitted to the drivetrain (similar to 'lugging'). The opposite of what TCC
'slippage' was intended to prevent.

Being prevented from altering TCM software program maps, I used intentional
induction of TCM limp home mode to turn off TCC control and used the TCC
adaptation feature to manipulate TCC control intensity and was able to produced
useful data.

Experimentation with damping and modification of TCC solenoid action optimized
what I believe to be the best 'compromise' between fuel economy and TOTAL
elimination of RSN. The patient's transmission now behaves like a Mercedes Benz
'S Class' transmission, smooth and seamless.

Ongoing clinical trials will hopefully reveal any detrimental effects on fuel
economy and any mitigating effects of long term TCM adaptation in reducing the
efficacy of 'the cure'.

RSN may not be of great concern to highway expediters but any Sprinter owner
transporting people in stop and go traffic will agree it is UNACCEPTABLE in a
vehicle of this sophistication and pricing as well as a concern with regards to
long term drivetrain damage.

Stay tuned for updates. Owners suffering with severe RSN are welcome to inquire
about participation in further clinical trials. Doktor A

Update: https://sprinter-source.com/forums/showpost.php?p=422714&postcount=8

Doktor A - what an impressive example of scientific deduction! I look forward to hearing the results of your additional testing. I have not personally experienced RSN and would be curious to find out why it is that some Sprinters are affected while others are not.

Tim

TimJuhl said:

I have not personally experienced RSN and would be curious to find out why it is that some Sprinters are affected while others are not.

Tim

Click to expand...

Most Sprinters are affected, but driving conditions and driver's driving style may partly mask or conversely, may even exaggerate the symptoms. I would be curious to instrument and observe a vehicle 'free' of RSN symptoms, if one truly exists.

Production tolerances as well as TCC adaptation are factors as well. The TCM has maps controlling TCC calibrated slip of Engine speed vs. Transmission input speed. The adaptation works to minimize the variation between actual slip and the map's desired slip. I used this adaptation feature to experiment and generate data. Doktor A

abittenbinder said:

Owners suffering with severe RSN are welcome to inquire
about participation in further clinical trials. Doktor A

Click to expand...

Wow, I want to participate. Let me know how. I'm in Southern NJ, will travel.

Is there any real data to support the theory that Short WB (118") suffer the most severe RSN?

David

I have RSN on my 06 140 high roof 2500 and await further info and maybe a trip to Doktor A's O.R.
One thing I have wondered about is to use a marine product called a " Drive Saver " which is a flex coupling that goes between the trany output flange and the propeller shaft flange. Their primary purpose is to prevent damage to the engine/trany by breaking if the prop hits a rock or log etc. They are made in different sizes to match the flanges and available for even high power engines.
The MB cars I've been under have flex couplings at both ends of the drive shaft, but they seem to have a fabric re-enforced rubber flexing element in them where as the Drive Saver seems to be just a urethane element.
Benefits might be less RSN and maybe reduced noise by decoupling the engine from that long resonator tube of a drive shaft.
I could see some possible serious problems as well. Durability of the unit with failure causing a dangling drive shaft!! Also can the splined couplings on the shaft absorb the .75/1 " thickness of the Drive Saver without the overall length of the shaft being to great?
Perhaps the flex coupling from a MB car would fit.
Any thoughts?

Thanks Bob

Very interesting news indeed from The Global Sprinter Research Center.

A further data point that may or may not be germane: Experimenting with cruise control the other day, I was using the "nudge" feature to see how low a speed I could maintain while still in cruise. On an empty, smooth road and beginning at 30 mph, I had "nudged" it down to 18 mph and was still in cruise mode when I began to experience driveline resonances very similar to RSN. I heard and felt a low, groaning noise that repeated about once every 30 seconds or so. After a few cycles of this behaviour, I terminated the experiment.

Andy,

Interesting results. We have run similar tests on our Dyno using 3 different Sprinters, 2 with RSM and one without. Running vehicles on our Dyno allows us to concentrate on the readings instead of running into someone or something. We have been able to pay close attention and in all cases have found the torque converter activated in 3rd -5th gears under normal driving conditions. We have not seen the converter being activated during acceleration in all 5 gears. We have seen the converter remain activated on deceleration down into second gear and in some occasions not releasing until 1st gear. On highway testing with a co-driver monitoring the scan tool confirms the above information. Our factory DAS scan tool allows resetting of the TCM and the running of a new shift adaptation program. As had been noted in past threads, running several adaptation programs made no difference in RSN. I hope this information helps.

Thank you, John
Sprinter Store
http://sprinterstore.com/
A division of Upscale Automotive, Inc.
19460 SW 89th Ave.
Tualatin, OR 97062
503-692-0846

abittenbinder said:

Here at the Global Sprinter Research Center, I am happy to announce a cure for
Rumble Strip noise. Longer term 'Clinical trials' are now in progress and
looking promising.

Mbenz's use of 'controlled' TCC slippage was intended to allow controlled
bypass of fluid to the transmission cooler so as to reduce temp of both the
fluid and the torque converter and IRONICALLY to dampen engine torsional
vibrations. I put the word 'ironic' in capital letters because under certain
conditions, the opposite appears to occur.

Doktor A

Click to expand...

Finally, a cure to the RSN! However I do not agree with the good Doktor's use of "ironic" The ironic part is how MB did not research the problem and fix the problem. It was left to a small one-man shop to figure how to fix the problem. This should have been a warrenty repair, but as those of us who have RSN are aware, MB denies the problem. When the problem is acknowleged, there is no permanant repair. I did have my 2003 fixed under warrenty. The TCM was replaced and the problem was fixed for approximatly 1/4 mile. I never wasted my time trying to get the2006 RSN repaired.

Congratulations to the Doktor for fixing something the engineers could not fix. Is this something that can be fixed w/o a trip across the country to Doktor A shop?

dbeyer said:

Wow, I want to participate. Let me know how. I'm in Southern NJ, will travel.

Is there any real data to support the theory that Short WB (118") suffer the most severe RSN?

David

Click to expand...

I will contact you regarding participation in further trials.

Regarding further trials-Efficacy of the fix is not in question-IT WORKS, but as I mentioned in the opening post I am interested in any possible detrimental changes in fuel economy and does longer term adaptation of TCC action possibly reduce the overall effectiveness of the 'fix'. Doktor A

pvsprinter said:

I have RSN on my 06 140 high roof 2500 and await further info and maybe a trip to Doktor A's O.R.
One thing I have wondered about is to use a marine product called a " Drive Saver " which is a flex coupling that goes between the trany output flange and the propeller shaft flange. Their primary purpose is to prevent damage to the engine/trany by breaking if the prop hits a rock or log etc. They are made in different sizes to match the flanges and available for even high power engines.
The MB cars I've been under have flex couplings at both ends of the drive shaft, but they seem to have a fabric re-enforced rubber flexing element in them where as the Drive Saver seems to be just a urethane element.
Benefits might be less RSN and maybe reduced noise by decoupling the engine from that long resonator tube of a drive shaft.
I could see some possible serious problems as well. Durability of the unit with failure causing a dangling drive shaft!! Also can the splined couplings on the shaft absorb the .75/1 " thickness of the Drive Saver without the overall length of the shaft being to great?
Perhaps the flex coupling from a MB car would fit.
Any thoughts?

Thanks Bob

Click to expand...

If fuel economy with my RSN 'fix' remains acceptable you will not have to worry about the costs, complexities and possible efficacy of introducing a drivetrain 'weak link' in the form of a flex coupling. Lets see how the long term trials progress. Doktor A

Doktor A. this is great news, and long term testing results will be much appriciated. I have attatched a fliud flow schematic (I am sorry its in Word, but my PC is old and out of date). The schematic is for EMCC in 5th gear. I guess my question is could there be more than just aggressive programming involved, or could there actualy be an issue with the TCC regulator valve, or applicable circuits and components? Could the adaptation be temporarily masking the issue? By looking at the schematic I am wondering if the TCC control valve spring is becoming "weak" and allowing the pressure from the TCC solenoid to move the valve too far during slow speeds thus applying too much line pressure to the converter clutch causing it to slip less during these manuvers.

Carl
View attachment emccflow.doc

glasseye said:

Very interesting news indeed from The Global Sprinter Research Center.

A further data point that may or may not be germane: Experimenting with cruise control the other day, I was using the "nudge" feature to see how low a speed I could maintain while still in cruise. On an empty, smooth road and beginning at 30 mph, I had "nudged" it down to 18 mph and was still in cruise mode when I began to experience driveline resonances very similar to RSN. I heard and felt a low, groaning noise that repeated about once every 30 seconds or so. After a few cycles of this behaviour, I terminated the experiment.

Click to expand...

Thanks for the 'data point'. What you experienced is likely the 'lugging' -like effects of the overly aggressive activation of the TCC at very low speeds and loading.

The mapping was likely 'over-done' in the name of maximum fuel economy and to hell with drive line sophistication. Doktor A

scubanw3 said:

Andy,

Interesting results. We have run similar tests on our Dyno using 3 different Sprinters, 2 with RSM and one without. Running vehicles on our Dyno allows us to concentrate on the readings instead of running into someone or something. We have been able to pay close attention and in all cases have found the torque converter activated in 3rd -5th gears under normal driving conditions. We have not seen the converter being activated during acceleration in all 5 gears. We have seen the converter remain activated on deceleration down into second gear and in some occasions not releasing until 1st gear. On highway testing with a co-driver monitoring the scan tool confirms the above information. Our factory DAS scan tool allows resetting of the TCM and the running of a new shift adaptation program. As had been noted in past threads, running several adaptation programs made no difference in RSN. I hope this information helps.

Thank you, John

Click to expand...

Thanks for your input. I don't know how you missed observation of TCC activation in all forward speeds.

To prevent confusion to readers- The 'resetting of the TCM' John refers to is reset of adaptations, not any internal mods of TCM pre-programed mapping. The DRBIII and SDA allow the same resetting of long term adaptations.

My use of the TCM's adaptation of the TCC control pressure was for experimental observation. I was able to create more severe forms of RSN and then return them back to 'normal' RSN. I did not use reset of adaptations nor tedious 'relearning' of adaptation to attempt total elimination of RSN. You're right, we know from years of experience that does not work. Doktor A

abittenbinder said:

but as I mentioned in the opening post I am interested in any possible detrimental changes in fuel economy and does longer term adaptation of TCC action possibly reduce the overall effectiveness of the 'fix'. Doktor A

Click to expand...

Andy,
I'm willing to live with reduced fuel economy.

To prevent/reduce RNS I manually over ride the mapping by shifting (bumping) every gear up in acceleration and down shifting every gear during deceleration. My RNS is greatly reduced my running higher RPMs than the auto mapping. My fuel economy has increased slightly. I can't get the TCC to adapt to the higher RPM shifting, so hopefully it won't adapt to over ride your fix.



David

Douglas Hicks said:

Finally, a cure to the RSN! However I do not agree with the good Doktor's use of "ironic" The ironic part is how MB did not research the problem and fix the problem. It was left to a small one-man shop to figure how to fix the problem. This should have been a warrenty repair, but as those of us who have RSN are aware, MB denies the problem. When the problem is acknowleged, there is no permanant repair. I did have my 2003 fixed under warrenty. The TCM was replaced and the problem was fixed for approximatly 1/4 mile. I never wasted my time trying to get the2006 RSN repaired.

Congratulations to the Doktor for fixing something the engineers could not fix. Is this something that can be fixed w/o a trip across the country to Doktor A shop?

Click to expand...

That's a good question.

Even though I have spent significant time in research and testing of RSN, I do recognize that keeping a 'fix' close to the vest and only available to my clientele would not be fair to others unable to trek here to Pennsylvania.

I hope to recoup some costs and am thinking of making a DIY kit for people unable to visit me. But first we must explore any fuel consumption side effects. Stay tuned. Doktor A

sprintguy said:

Doktor A. this is great news, and long term testing results will be much appriciated. I guess my question is could there be more than just aggressive programming involved, or could there actualy be an issue with the TCC regulator valve, or applicable circuits and components? Could the adaptation be temporarily masking the issue? By looking at the schematic I am wondering if the TCC control valve spring is becoming "weak" and allowing the pressure from the TCC solenoid to move the valve too far during slow speeds thus applying too much line pressure to the converter clutch causing it to slip less during these manuvers.

Carl

Click to expand...

Carl, Keep in mind that most all RSN cursed vehicles arrived that way from day 1. I did however explored those very variables you mention. I found no significant difference in spring tension between new and high mileage TCC control valve springs.

Keep in mind that production tolerance variations and aging of components (springs are one example, solenoid action another) is the very reason adaptation is employed in the TCM. As I said, adaptation helps keep engine rpm/trans input shaft rpm maps in synch with actual speed relationships.

The 'fix' not only alters the implementation of those maps but also damps the solenoid action which is duty cycling the TCC when in its slip (on) mode. Doktor A

dbeyer said:

Andy,
I'm willing to live with reduced fuel economy.

To prevent/reduce RNS I manually over ride the mapping by shifting (bumping) every gear up in acceleration and down shifting every gear during deceleration. My RNS is greatly reduced my running higher RPMs than the auto mapping. My fuel economy has increased slightly. I can't get the TCC to adapt to the higher RPM shifting, so hopefully it won't adapt to over ride your fix.

David

Click to expand...

Well in that case do I have a fix for you! However, it appears you won't be very helpful in fuel economy feedback since you have not been driving 'normally'. Your fuel economy may actually improve.

I suspect long distant highway expediters will not be interested in any RSN reduction because it normally appears at lower speeds and loads. However there are many owners who drive stop and go routes who will welcome the "S-Class' smoothness.

The driving style adaptation you are hoping will 'adapt to higher RPM shifting' is a short term adaptation feature which disappears when 'normal' driving style resumes or ign key reset takes place. The adaptation I refer to is a long term wear and tear. The NAG1 TCM has 4 levels of adaptation. Doktor A

I guess my initial understanding of what you performed for testing and repair was misdirected.
Did you use the DRBIII for the adaptation of the TCC solenoid. I ask because I never noticed that function before (but I could have not been looking). Or was it by putting the TCM into failsafe mode at a certain frequency of the TCC solenoid that altered the adaptation? This is what is now unclear for me.
If you don't want to answer that I understand, I too play close to my chest sometimes until everything is washed out.

Carl

sprintguy said:

I guess my initial understanding of what you performed for testing and repair was misdirected.
Did you use the DRBIII for the adaptation of the TCC solenoid. I ask because I never noticed that function before (but I could have not been looking). Or was it by putting the TCM into failsafe mode at a certain frequency of the TCC solenoid that altered the adaptation? This is what is now unclear for me.
If you don't want to answer that I understand, I too play close to my chest sometimes until everything is washed out.

Carl

Click to expand...

Ah, a poker player.

Reset of adaptations feature resets fill time and pressure of clutch pistons, shift overlap and shift solenoid working pressure (shift time) AND TCC adaptation, to factory baseline settings.

TCM limp home default mode completely shuts off TCC activity. Doktor A

Now I understand .. good info

P.S. You are a credit to the repair and research industry. Thanx

Carl