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Floobydust
Veteran
Date registered: Mar 2014
Location: Massachusetts, USA
Vehicle(s): 1995 E320 Cabrio, 2003 G500, 2000 SL500, 1980 TR8
Posts: 284
| RE: New to the G, but not to MB . . .
Well, I got the truck back from the dealer and to make a long story short, they were unable to find the source of the thrumming. I have to say that they put a huge amount of time and personal investment into looking for it, but they didn't hit me for a huge bill. I know it had to be money loser for them, but their commitment to finding the problem couldn't have been better.
They did rule out tires as the source of the issue because they swapped tires from a new g with no issues (one that belongs to a friend of the server manager who asked the friend for the favor) and the thrumming remained in my truck. Interestingly, the new Gs are coming with Khumo tires instead of Geolanders.
At the end of the day, their best guess is the transfer case, but they are not confident enough of that to say replace it. They recommended just driving it until it gets worse (kind of what I have been dong) so that a more positive diagnosis can be made.
While the G was there, I happened to be looking at some threads on the transfer case and one of them discussed TC oil. The MB recommended oil for my G500 is Synthetic SAE 75W-90 which is what I have in there. But I also noticed that for the G55 (with the same transfer case and differentials), MB recommended SAE 75W-140. This make sense given the extra power that the TC sees in an AMG model. But it occurred to me that I could use this in my mere mortal G500 with perhaps at most a small fuel consumption penalty (and let's face it, a small decrease from abysmal to more abysmal isn't really going to make a difference). I have noticed that the thrumming only starts after driving for a few miles, so I'm thinking that when something heats up, it gets lose.
So today, I changed my TC fluid to the AMG 75W-140 thinking that the extra viscosity at temperature might help. I haven't had a chance to really evaluate if it made a difference, but I will report back, plus or minus. If it does quite down, the dealer may be correct of the TC case being the issue.
- FD
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MiN
Extreme Veteran
Date registered: May 2006
Location: Alpujarras, Spain
Vehicle(s): No cars, at all.
Posts: 555
| Re: New to the G, but not to MB . . .
The 75W-140 is for the axles only on the AMG model. The T/C case takes the same 75W-90 synthetic as the other models. |
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Floobydust
Veteran
Date registered: Mar 2014
Location: Massachusetts, USA
Vehicle(s): 1995 E320 Cabrio, 2003 G500, 2000 SL500, 1980 TR8
Posts: 284
| Re: New to the G, but not to MB . . .
This is the reference I used for that information. It says at the bottom of page 1 that for Model 463.270/271 (G55) the VG 150 E transfer case should use 75W-140. Interestingly, they specify 75W-140 only for the rear differential. It seems 75W-90 is okay for the front diff.
By way of an update from my commute in this morning, the 7W-140 seems to help a little, but the thrumming is still there. I'll just have to see how it goes.
Attachments
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 spec_sheet_231.1_2012.pdf (17KB - 13 downloads)
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DUTCH
Administrator Doppelgänger
Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9963
| Re: New to the G, but not to MB . . .
I think you're mis-reading that spec.
The 2010 G-Class Owners Manual specs the same TC fluid for both the G550 and the G55AMG. The P/N is A.001.989.28.03, which is an 85W90 transmission oil.
It also specs Castrol SAF-X for both the front and rear axles/diffs in the G55AMG. It is a 75W140 gear oil. |
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MiN
Extreme Veteran
Date registered: May 2006
Location: Alpujarras, Spain
Vehicle(s): No cars, at all.
Posts: 555
| Re: New to the G, but not to MB . . .
It's easy to mis-read. Having done all my own maintenance on a 2005 G55 for 5 years, I made sure what went where was right. |
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Floobydust
Veteran
Date registered: Mar 2014
Location: Massachusetts, USA
Vehicle(s): 1995 E320 Cabrio, 2003 G500, 2000 SL500, 1980 TR8
Posts: 284
| RE: New to the G, but not to MB . . .
Interesting. . . The manual in my 2003 doesn't really say much about the G55 because in that year it was just a G500 with an extra 1/2 liter of placement. The real power didn't start until supercharging. The document(s) I have are all copyright MB, so they come from the source, so I'm curious how they should be read. Given what has been posted about what is noted in the later G55 manuals, I'm not sure what to make of the section, "Model 463.270/271 - 75W-140" in these documents. Is there an error in the documentation?
Interestingly, the thrumming noise is significantly improved (but not banished) with the new oil in it. Given the way multi-grade oils work, I'm not sure what the downside would be of running the heavier oil. I'd be curious what people have say about this.
edit:typos
Edited by Floobydust 11/10/2014 2:37 PM
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Floobydust
Veteran
Date registered: Mar 2014
Location: Massachusetts, USA
Vehicle(s): 1995 E320 Cabrio, 2003 G500, 2000 SL500, 1980 TR8
Posts: 284
| RE: New to the G, but not to MB . . . update
I wasn't able to track down the reasons for the dichotomy between the later AMG owners manuals and the MB engineering sheets for lubricants, so I changed the transfer case oil back to the 75W-90. I can still use the 74W-140 in the differentials according to both sources.
As I posted earlier, the dealer was not able to track down the source of the noise, so I took some unorthodox steps to track things done, or at least rule out certain components as the source. I realized that the TC is located just in front of the battery box and the transmission rear bearing is right behind the small removable carpet panel in the passenger foot well. So I removed the battery cover and the carpet piece and drilled a 1/8" hole through the sheet metal in each location. This allowed me to insert an automotive stethoscope through the hole and contact the TC and the transmission. With the scope inserted through the hole (and a friend driving) I was able to both hear the sounds of the gears running and feel the TC move as we drove. I could hear nothing but the sound of fine running machinery nor could I feel any movement associated with the vibration/noise. I was, in fact quite surprised by how smooth both boxes ran. I sealed the holes with small rubber plugs carried by our local hardware store (the old fashioned kind with lots of actual hardware).
So I can now say that the source of the noise is not the TC, the transmission, the homekinetic shaft, nor either driveshaft. It isn't the tires either as I also picked up another set of 2007 wheels and slightly larger tires (along with a genuine brush bar and LED DRL headlight surrounds) and the noise is exactly the same with the new tires, although the speed that it occurs at is slightly lower as would be expected from the larger tires (~6% speedo error with those tires). I know it is unlikely, but is there a tire size setting in SDS/DAS that would allow this speedo error to be corrected?
So it must be in one of the two axles. I'm still inclined to suspect the front axle, but I will "sound" each axle in turn to further narrow it down. I have inspected the rear diff and it looks good with no metal bits or signs of wear on the ring gear. I'm going to inspect the front next weekend (have to use a friend's lift).
 (Probe 02.jpg)
 (Probe 04.jpg)
 (Probe 06.jpg)
 (Probe 07.jpg)
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Probe 02.jpg (301KB - 0 downloads)
Probe 04.jpg (326KB - 0 downloads)
Probe 06.jpg (340KB - 0 downloads)
Probe 07.jpg (337KB - 0 downloads)
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shochu
Extreme Veteran
Date registered: Jul 2006
Location: Jakarta, Indonesia
Vehicle(s): indonesian-assembled '97 G300
Posts: 452
| Re: New to the G, but not to MB . . .
that's perseverance..  |
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Floobydust
Veteran
Date registered: Mar 2014
Location: Massachusetts, USA
Vehicle(s): 1995 E320 Cabrio, 2003 G500, 2000 SL500, 1980 TR8
Posts: 284
| RE: New to the G, but not to MB . . .
Well, I'm still at it. The suspension vibration has been banished through bushing replacement, but the drive train vibration is still there. I used a portable DSO and a home brewed magnetic vibration sensor to try and localize the source. From these measurements (see pics), it really seems that the front axle is where the vibration is originating. Note that when looking at the traces, the "vibration" is not the higher frequency sine wave, but rather, the "envelope" that results from the higher frequency sine wave being modulated by the actual, low frequency, vibration.
I have also observed that the drive train vibration does not occur immediately, but only after the truck has been drive several miles at speed, which suggests to me that something is heating up and allowing more "play" somewhere. In addition, the vibration is usually more severe during declaration than during cruise or acceleration.
The combination of all of these observations is making me suspect that there is a problem with the pinion bearings in the front differential. Is there a way to inspect/evaluate/test the pinion bearings without a total axle tear down?
Thanks,
- FD
 (Front Axle.jpg)
 (Rear Axle.jpg)
Attachments
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Front Axle.jpg (91KB - 0 downloads)
Rear Axle.jpg (84KB - 0 downloads)
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atg
Veteran
Date registered: Nov 2014
Location: Los Angeles
Vehicle(s): 2005 G55, 1985 300tdt
Posts: 129
| Re: New to the G, but not to MB . . .
Sorry but did you run the truck up on a hoist and just listen to everything with a stethoscope with it in gear? |
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Floobydust
Veteran
Date registered: Mar 2014
Location: Massachusetts, USA
Vehicle(s): 1995 E320 Cabrio, 2003 G500, 2000 SL500, 1980 TR8
Posts: 284
| RE: Well, I think I've found it
The vibration is coming from the front of the transfer case. I over looked an key characteristic of both my vibration sensor and the mechanics stethoscope along the way and that started to lead me down the wrong path. The key characteristic is that they only sense vibration in the axis that is Normal to the point of contact. Lateral (in the X or Y direction) is not well sensed. When I attached the electronic sensor (using its magnetic base) to heads of the transfer case bolts which effectively allowed it to sense vibration only in the front-to-back direction. The same thing was happening with the stethoscope because I was "sensing" the transfer case in a nearly horizontal axis.
Once a realized my oversight, I checked the X, Y, and Z axises on the front and back of the transfer case and it was immediately apparent that the front of the transfer case is vibrating in the X-Y plane when the "vibration" occurs. To confirm my finding, I shaped a wooden block that allowed by to effectively restrict the movement of the front TC bushing and the "vibration" was suddenly many times more prominent. None of the other characteristics (speed, acceleration versus deceleration) changed, so I'm sure this is the point of origin.
So now the question is, what is causing the front end of the TC to vibrate? The X-Y plane mode seems to me to point to either a shaft that is out of balance or a shaft that is not running true to center (e.g., worn bearings).
As I think most of you know, I replaced the homekinetic shaft with a genuine MB one due to a bad rear CV joint which I originally though was the source of the vibration. But the shaft change did not improve the vibration issue. I noted MB no longer provides the "green dots" on the HK shafts to line up of the marks on the flanges. According to the technician I spoke with, a specific rotational orientation is not necessary - they new HK shafts should work in any position. Should I believe that? I have been thinking about rotating the HK shaft 180 degrees to see if things change. I would follow the same procedure that MB says to use for the drive shafts.
My other thought is that the the bearings on the input shaft of the TC were damaged by the bad CV joint - especially if the previous owner drove it that way for a while. This kind of fits with the observation that the vibration doesn't start until the truck has been driven a few miles. I'm not sure how to test/measure for this.
Sorry for the long winded post, but I wanted to get people's thoughts on it. Have I overlooked anything? Any suggestions?
Thanks!
- Scott
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| RE: New to the G, but not to MB . . .
I'll put my vote in with the "orientation of a new HK shaft doesn't matter. The rebuilt one that Vadim and I put into my G is very smooth and we paid no attention to orientation. I suppose there is a 1-in-36 chance the we put it in "right" by accident. As to the vibration. Have you checked the runout of the TC input shaft?
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Floobydust
Veteran
Date registered: Mar 2014
Location: Massachusetts, USA
Vehicle(s): 1995 E320 Cabrio, 2003 G500, 2000 SL500, 1980 TR8
Posts: 284
| RE: New to the G, but not to MB . . .
AlanMcR - 12/15/2014 1:46 AM
Have you checked the runout of the TC input shaft?
I would love to check the run out, but the documentation I have (or can find) only covers the old style 8-bolt flange and requires a "special tool" to check the run out. I suspect that measuring the new style also requires a special tool. I can't find a spec for the HK shaft flange run out either. If anyone has a spec/procedure that I can do, it would be very much appreciated. I have the dial gauges, mounts, etc.
BTW, does it matter which end of the HK shaft is the "front" and which is the "back"? The three ribs on the shaft itself are not in the center (although I think they are on the shorter 500GE HK shaft), so there may be an orientation, but I would doubt it.
Thanks! |
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| RE: New to the G, but not to MB . . .
The shaft is symmetrical.
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H1LM002G55
Expert
Date registered: Mar 2010
Location: S Florida / Geneva / Jeddah
Vehicle(s): 500 GE, G55, LM002, H1
Posts: 1796
| Re: New to the G, but not to MB . . .
Floobydust- PM Sent. |
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