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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| Transfer Case in Neutral - let's get scientific
I've got the dreaded TC in Neutral problem, and this time, it really is in neutral, not just pretending to be in the display.
After a bit of "diagnosing", I've found that my TC is OK, the motor is OK, the Hall position sensor is sending pulses and a direction signal, and the TC control module seems to be working if I first reset it with the star system to "base function". However, it fails the "adaptation" menu in the Star set up. Says the learned distance is too long. Sometimes says its too short. Without adaptation, the control module will just jam the motor round full tilt until it stalls, in H or L position, which is good for getting moving, but probably not good for wear and tear. After adaptation, it is supposed to know and remember just how far to go, and then back it off a little so its not tight against the limit.
After searching the threads, I found a lot of contradictory information eg was there a TSB on this? Seems not. Do 2004 and later years have the problem? So I'd like to gather up some proper first hand info.
If you have a G with electric H / L selection on the TC, any year, please reply with:
Year of manufacture
Do you get the "blank square" sometimes where it should say H or L?
Does it really go into N when the square is blank?
Have you had any parts replaced (TC, TC module, switch, Servo motor). Part numbers for a bonus.
Would particularly appreciate replies from people who have had no problems, as this might help eliminate things. For example, the part number for the Servo Motor has never changed, so I suspect that part is not to blame, although Merc replaced a lot of them on 2002 model years. The control module has been through many revisions.
If possible, I'd like to really figure this out. Seems like Merc wasted a lot of time just replacing things, without getting to the bottom of it.
Thanks in anticipation.
Edited by W5YK 8/27/2009 6:44 PM
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ewalberg
Expert
Date registered: Apr 2006
Location: Past: San Francisco. Present: Germany
Vehicle(s): 2000 g500
Posts: 1887
| Re: Transfer Case in Neutral - let's get scientific
If it's sometimes saying too short and sometimes saying too long it would make me think there's an issue with either the sensor or unit interpreting the data... that is unless they're brute forcing it and just using motor current to know when it's reached one limit or another. Considering how the Throttle Position Sensor still largerly works most of the time and yet it can still intermittantly crap out, it sure wouldn't surprise me if you've got a sensor issue despite finding that the sensor is sending pulses... just a thought. Good luck with it....
Oh, you know you might also want to post this on benzworld since it's mostly mbusa trucks there...
Edited by ewalberg 8/27/2009 7:29 PM
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| RE: Transfer Case in Neutral - let's get scientific
I also fail to qualify for your survey, but I have an opinion none the less: Hall effect sensors and microprocessors are unlikely to fail. The connection(s) between them are a likely candidate though. Relating this back to the TPS sensors, I suspect that some of the replaced TPS sensors only helped because the contacts were renewed by the replacement. Perhaps MB failed to properly condition the hall effect sensor signal. Once the connection is compromised the circuitry gets a a weak or noisy signal and problems ensue.
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fernweh
Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
| RE: Transfer Case in Neutral - let's get scientific
Richard,
I have a problem with the TC in my 2004 G500 as well.
Right now the "Visit the Workshop" message is displayed quite often.
The display is mostly blank, but still the TC is in street gear - never in Neutral. I also get the message like "shift not completed". I can reset the TC from inside the truck - have not used the Star system yet.
I do believe the wire harness connection might be the culprit here and I will look at that during the next (soon to be) maintenance.
If you need to know anything more specific, please contact me.
Karl |
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Indiana Drew
Expert
Date registered: Feb 2007
Location: Houston Tx
Vehicle(s): 2002 G500 LWB, 1980 280GE SWB (Sold), S500
Posts: 2223
| RE: Transfer Case in Neutral - let's get scientific
fernweh - 8/27/2009 6:52 PM Richard, I have a problem with the TC in my 2004 G500 as well. Right now the "Visit the Workshop" message is displayed quite often. The display is mostly blank, but still the TC is in street gear - never in Neutral. I also get the message like "shift not completed". I can reset the TC from inside the truck - have not used the Star system yet. I do believe the wire harness connection might be the culprit here and I will look at that during the next (soon to be) maintenance. If you need to know anything more specific, please contact me. Karl Mine too: 2002 Often the blank square, but always in H, never in N Sometime the "Sift Not Complete" message, but if I switch to low and then back to high it goes back to normal for at least a short time ... My issue is still with the locker, but that is another thread ... Oh and I don't recall having any TC parts ever being replaces ...
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Otiswesty
Administrator
Date registered: Jun 2007
Location: Portland, Oregon
Vehicle(s): 463.241, 461.213
Posts: 3004
| RE: Transfer Case in Neutral
Mine is a 2002 G500
When I first bought the truck, the TC display was often blank but drove in high gear. It seemed to occur more commonly if I had not driven the truck for a week or two, but I'm not completely sure on that. I was able to switch between high and low with the occasional failure. I had two occasions while driving that the TC went into a freespooling true neutral, and I was disabled. The first time I was able to reengage high after multiple attempts and power cycling the system. The second time, I had the G flatbed towed to the dealer and they diagnosed a bad TC control module and replaced it with a "3rd generation" TC control module. I will try checking the repair paperwork tomorrow for a part number, but I remember it costing a bit over $300 including installation and diagnostics.
Last weekend at NW Mogfest, I was switching H-L-H quite a bit on the fly without any issues. I have also not seen a blank screen in the TC indicator since the repair was made 4 months or so ago.
I have not attempted to put the TC in neutral since it was repaired, so I can't comment on that screen indicator. |
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MarcO
Elite Veteran
Date registered: Apr 2006
Location: Irvington, NY
Vehicle(s): G 500 SWB, Volvo XC90 V8
Posts: 835
| Re: Transfer Case in Neutral - let's get scientific
Both my '02's had to have the TC module replaced. The servo was not the problem. Once the module was replaced the problem (blank box and or real neutral) never happened again. |
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abp
Regular
Date registered: Dec 2006
Location: Pasadena, California
Vehicle(s): 1982 300CD
Posts: 60
| Re: Transfer Case in Neutral - let's get scientific
mine is a later 2003.
I get the blank square fairly regularly these days. It has never been stuck in neutral though, and I can usually get the H back if I toggle from low back to high. Being the 2nd owner, I don't believe the anything has been changed. But as it is happening more and more frequently these days, I'm sure the time is coming quickly to do so.
Edited by abp 8/28/2009 1:17 PM
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djdinaz
Extreme Veteran
Date registered: Jun 2007
Location: Arizona
Vehicle(s): 03 G55
Posts: 439
| Re: Transfer Case in Neutral - let's get scientific
Mine's a late 03 as well, never had the square, but, my service records show it being replaced a while ago. Unfortunately, there's no part number listed.
Looking at a number of the various 463's (246, 249, 270, 333, etc) in the EPC, it would seem that there have been at least 4 TC modules (group 54, subgroup 080 in EPC):
A463 545 0832 (earliest edition)
A463 545 2132
A463 545 2532
A463 545 2732
This particular part is buried down inside the mess of control units in the center console, and I suspect difficult to get at to see a part number. I wonder if one of our resident parts suppliers could chime in on compatibility between the various iterations, as it seems this is the culprit (because of all the revisions that have occurred).
Also, in looking at the servo motor, A4635400088, that part appears to not have changed at all, there are no revisions listed for it. The transfer case on my datacard shows 750.654, and in looking at the data card on a '09, it lists the same model. Knowing that in 6 years, they're still using the same part with no listed revisions, I really think that the servo motor is not at fault here.
Edited by djdinaz 8/28/2009 2:16 PM
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: Transfer Case in Neutral - let's get scientific
Karl,
One thing I discovered is that you only get the "visit workshop" message if you disconnect the servo motor from the control module. You may have a bad harness, or it may just be that the connector on the servor motor is not pushed completely on. When I was testing my servo motor, I found that it had not been pushed on all the way, and was not mechanically "latched". There is a large rubber seal that can get trapped and prevent the connector pushing on all the way. Worth checking.
Richard
 (TC visit workshop.jpg)
 (tc connector.jpg)
Attachments
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 TC visit workshop.jpg (34KB - 19 downloads)
tc connector.jpg (38KB - 19 downloads)
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: Transfer Case in Neutral - let's get scientific
Djdinaz,
I was thinking exactly the same way as you - the servo motor never changed, so it's not the culprit, and the control module went through umpteen revisions, so there's the problem
I got a new servo motor today, and here's a photo of the old and new...
They are different, even though the part number hasn't changed. The difference is that the splines that drive the shaft at the motor end have been beefed up considerably. You can't really see them clearly in the photo, as there is a cover, but the splines on the old motor are very small. The splines on the new version are exposed, and huge by comparison.
That turns out to be important - more details later!
Richard
Edited by W5YK 8/28/2009 3:44 PM
 (tc motors.jpg)
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tc motors.jpg (44KB - 26 downloads)
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fernweh
Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
| RE: Transfer Case in Neutral - let's get scientific
Thank you Richard,
I had suspected something like it and will crawl under the G-wagen over the weekend and check it out.
When the shift motor gets replace at the dealer the connection is being "worked" on, and a bad connection might be the only thing which is at fault here. Just a "small" $540.00 difference - hopefully.......
Karl |
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ChuckB02
Member
Date registered: Mar 2009
Location: San Diego
Vehicle(s): '04 UZJ100 (FJ60, UZJ100, FJ55 all sold...)
Posts: 41
| Re: Transfer Case in Neutral - let's get scientific
I have a quick question about shifting the t-case on Pre-MBUSA G's vs. 2002+. (sorry I don't mean to high-jack the thread)
I noticed in pictures that the pre-MBUSA G's have a manual shift-level to the rear of the transmission shift lever. I do not see this on the '02+ is the pictures that I have seen. How is the t-case actuated in the '02+ vehicles, via the command system? TIA. |
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| Re: Transfer Case in Neutral - let's get scientific
djdinaz - 8/28/2009 11:09 AM
A463 545 2732 This particular part is buried down inside the mess of control units in the center console, and I suspect difficult to get at to see a part number. I wonder if one of our resident parts suppliers could chime in on compatibility between the various iterations, as it seems this is the culprit (because of all the revisions that have occurred).
It is indeed very difficult to get at, you have to remove the console between the two front seats and then lift the fuse box out of the way, see photo. You can read out the part number of the installed module from the Star system also, if you don't need to physically remove it and replace it. I just tried out the A463 545 2732 (ie the latest version of the TC control module) on my 2002, and it works perfectly. I had been concerned about that, since I read a post from someone who found that version would not talk to his 2002 dashboard display to display H or L. I found that it does, but only after successfully completing the adaptation with the Star system. I got that module cheap on ebay (I think $150).
Edited by W5YK 8/28/2009 3:46 PM
 (tc module location.jpg)
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tc module location.jpg (55KB - 35 downloads)
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: Transfer Case in Neutral - let's get scientific
fernweh - 8/28/2009 12:27 PM
When the shift motor gets replace at the dealer the connection is being "worked" on, and a bad connection might be the only thing which is at fault here. Just a "small" $540.00 difference - hopefully.......
Karl
The servo motor is expensive from Mercedes (your figure is right). Maybe get it from Bosch? Here is the Bosch part number...
 (tc bosch.jpg)
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tc bosch.jpg (35KB - 34 downloads)
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: Transfer Case in Neutral - let's get scientific
I have fixed my TC, and in the process I think I have figured out what the general problem is that a lot of people are having with blank displays and occasional slippage out of H or L.
I got hold of a new module and a new motor, so I could do comparative tests on everything.
First thing I noticed is that the motors now have much bigger internal splines. I figured there must be a reason for that, Bosch isn't going to waste time redesigning it if there's no problems.
Found that I could get the splines on the old motor to slip past eachother just by gripping the shaft firmly when the motor was running. Loud click-click-click noise.
Put the old motor in the TC, and listening carefully during the Star "adaptation" process, I could hear the splines clicking past each other. That explains why the adaptation fails with the error message "distance too long". The motor should stall when it reaches each end of travel, so it can learn the distances. If the splines are weak enough to let the motor keep running even when the shift fork in the TC has stopped moving, then the adaptation times out and fails (it times out after about 2 seconds).
Replaced the motor with the new one, and the adaptation routine worked fine, and everything now works. Also replaced the control module with the latest version, and that works too.
I'll continue in the next post to look at what might causes the splines to fail (they are strong enough to do the shifting, but not strong enough to resist being continually thrashed against the end stop).
Edited by W5YK 8/28/2009 4:10 PM
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ewalberg
Expert
Date registered: Apr 2006
Location: Past: San Francisco. Present: Germany
Vehicle(s): 2000 g500
Posts: 1887
| Re: Transfer Case in Neutral - let's get scientific
Correct, the 02+ have an electronic control instead of manual lever, but it's changed via a separate stand alone button, not the command interface. |
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: Transfer Case in Neutral - let's get scientific
Continuing on what I discovered...
First of all, if the servo motor has splines that are failing, what symptoms would show up?
Well, the TC control module only "knows" the position of the shaft by keeping count of pulses coming from a Hall effect sensor on the motor. If the splines are slipping, then that method doesn't work any more. The motor is spinning, sending pulses, but it's not moving anything. The module doesn't know about the slipping, it just knows the motor is spinning. So pretty quickly, the shift fork in the TC is not where the module thinks it is, leading to unpleasantness.
If you never shift from H to L, you might think this would not affect you. But it does. The reason is that every time you turn on the ignition and engage D, the TC module does a quick confirmation that it is in the right position by running the motor back and forth a little, touching briefly against what it thinks is the end of travel and coming back a bit from that. If the splines are failing, then it's not going to find the limit of travel where it was expecting it, and then it no longer knows where it is. So you get a blank square instead of H or L in the display. Or possibly a TC in Neutral message if it came up with a new incorrect position that is close to where N is.
This is a process that would lead to progressive failure of the splines. Each time they slip, they wear a little more, making them more likely to slip next time. Each time the control module loses track of the position, it runs the risk of ramming the motor against the limit and causes more spline damage. This is a very unvirtuous cycle between the motor and the control module.
Once the process really gets going, the servo motor is bound to fail. The splines will get stripped to the point that they can't work at all, and no amount of resetting or re-adapting will fix it. How long that takes probably depends on just how much torque your particular motor can make, how strong the splines are in that batch, etc. So some may go forever, and some start to fail right away. If you never strip that first tooth, the process never gets going.
I suspect that the problem was exacerbated by faulty control modules in 2002. If the control module was not functioning correctly, eg miscounting pulses, or forgetting it's position, then it makes it more likely it will drive the motor to the end limit, and start stripping splines.
At some point, Merc started improving these parts. My servo motor was made in July 2003 (replacement of the original 2002 motor) and it was still too weak. The control module was also upgraded several times. I suspect you need to have a good motor and a good module to eliminate the problem, but I don't know which versions/dates would be good. The latest versions of both would be a good place to start.
Summary to follow, since all this is a bit techie.
Edited by W5YK 8/28/2009 5:33 PM
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djdinaz
Extreme Veteran
Date registered: Jun 2007
Location: Arizona
Vehicle(s): 03 G55
Posts: 439
| Re: Transfer Case in Neutral - let's get scientific
Thanks for the detailed information.
I checked the EPC using an 09 G55 VIN, and the 2732 TC controller is the one thats spec'ed for it -- I couldn't locate the part for the 550 with the 7 speed setup.
The 50 cent question is when did Bosch make the change to the servo gears -- and if one does end up having to make a similar replacement, how would you guarantee you're getting the latest iteration, especially when the part number hasn't changed? I'd hate knowing I shelled out 500+ for the same flawed design.
(much like our window regulators, it looks like a cheap piece of plastic is the root cause of another pricey repair). |
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: Transfer Case in Neutral - let's get scientific
Here's the summary:
If you are occasionally getting a blank box instead of H or L in the dash display, it is quite likely that the TC servo motor is starting to strip it's teeth, causing the control module to lose track of its position.
The process can only get worse over time. Ultimately, you will not be able to shift ratio. The TC may slip out of gear randomly, since the position of the shifter is less and less accurate over time.
The best solution is to replace the motor and the module at the same time with the current versions.
If you have a 2002 or 2003 G500, you should think about doing this pro-actively. The failure can be sudden, and leaves you stranded.
If your servo motor or module was replaced in 2003, it still might not be good enough.
If you are in a bind, you can get the car moving by resetting the control module to "base function" using the Star system. Then the module will ignore positioning info from the motor and will just ram the fork into position. That will not last forever, since the remaining splines will strip even quicker after that, but it might get you home from Baja. If you don't have a Star system, put 12V to the two outside contacts on the servo motor to ram it in gear, reverse polarity for the other gear (I tried this, it works).
Please keep posting your experiences. If enough people post, we might figure out that modules after version xyz and motors after date aa/bb/cccc work together OK, and those slightly-less-than-current versions are much cheaper on ebay than buying new ones.
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