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  #1  
Old 11-02-2013, 07:35 AM
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Is {Mercedes} differential assembly friction really 40 - 90 Nm {not Ncm}?

G'day Folks,

I'm in the middle of rebuilding a W201 differential and I've come up with a little bit of a documentation puzzle.

The FSM could be correct but then again it strikes me as a possible error - I just don't have the experience of pulling these things apart so I need to check.

The FSM chapter 35-560 says that you should assemble the differential gears and shim them so that you achieve an assembly frictional torque between 40 and 90 Nm

Here's a link to the PDF on startekinfo

http://www.startekinfo.com/StarTek/outside/11832/Resources/201Create/PDF/10006.pdf

And here's a screen shot of the bit I mean



There's no way you could turn these gears with your fingers if that assembly torque was applied. On the one hand it seems like a lot of friction - on the other hand I can imagine how noisy a looser assembly might be.

I'm trying to reduce the (famous) W201 differential noise by rebuilding (see The W201 differential refresh thread)


I've checked the equivalent chapter in the W123 FSM and that too has a similar value. This adds credence to the value - but whoa this will make reassembly more problematic...

...so question is -

does anyone know for sure if this assembly frictional torque is correct?

Attached Thumbnails
Is {Mercedes} differential assembly friction really 40 - 90 Nm {not Ncm}?-w201-differential-assembly-friction.jpg  
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #2  
Old 11-02-2013, 09:39 AM
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The document i send you a while ago says a other value. i'm clueless so i dont know if its correct.

185mm dif?


168mm dif?
Attached Thumbnails
Is {Mercedes} differential assembly friction really 40 - 90 Nm {not Ncm}?-friction.jpg   Is {Mercedes} differential assembly friction really 40 - 90 Nm {not Ncm}?-friction1.jpg  
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  #3  
Old 11-02-2013, 11:01 AM
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Thanks supercow - you are a gent. The information you sent does indeed confirm those numbers in the FSM but the stuff you've just posted is for the pinion and this friction is for the for the output drive shaft (well the bit that the output shaft connects to).

I'm just wondering if 40 to 90 Nm is right.

I guess it is and I'll have to suck it up and see if it is possible to achieve. I suppose the differential needs a certain amount of resistance between the "spinability" of the rear wheels...
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #4  
Old 11-02-2013, 12:56 PM
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I think I was confused because post #2 is for something different than what you are referring to. In my experience with differentials (only about 60 years) I have never seen spider gears set up tight. I have no idea what they are trying to say when they are referring to 90 Nm to turn one of the side gears. I hope someone can explain it. I can't see how it would be possible to assemble the spider gears in the carrier under that much pressure. The only thing I can think of is if it were a posi-traction differential then that would be the torque to make the clutches slip. But the pictures they are showing are of a conventional differential I believe.

Paul
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  #5  
Old 11-02-2013, 01:34 PM
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EDIT - removed a bit to avoid confusion

Quote:
Originally Posted by pmckechnie View Post
I think I was confused because post #2 is for something different than what you are referring to. In my experience with differentials (only about 60 years) I have never seen spider gears set up tight. I have no idea what they are trying to say when they are referring to 90 Nm to turn one of the side gears. I hope someone can explain it. I can't see how it would be possible to assemble the spider gears in the carrier under that much pressure. The only thing I can think of is if it were a posi-traction differential then that would be the torque to make the clutches slip. But the pictures they are showing are of a conventional differential I believe.

Paul
Do you think PTFE bearings - as in seating of new PTFE bearings is a good enough reason?

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Last edited by Stretch; 11-02-2013 at 02:45 PM. Reason: Taken out a quote from a post that has now been removed
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  #6  
Old 11-02-2013, 01:36 PM
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Stretch:

The FSM for the 185mm and 210mm diffs. gives the following torques:

Open diff.: 15-20Nm (up to 35 where binding occurs)

Limited slip diff.: 25-35NM (clutch pack breakaway)
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  #7  
Old 11-02-2013, 02:46 PM
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Quote:
Originally Posted by Frank Reiner View Post
Stretch:

The FSM for the 185mm and 210mm diffs. gives the following torques:

Open diff.: 15-20Nm (up to 35 where binding occurs)

Limited slip diff.: 25-35NM (clutch pack breakaway)
Thanks Frank - do you happen to know if those (different) differentials also have these PTFE bearings?
__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #8  
Old 11-02-2013, 03:11 PM
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Your reference to the PTFE (Teflon) bearings I'm assuming is to coating on the cupped thrust washers?

No mention of same in the manuals which I have.
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  #9  
Old 11-02-2013, 05:34 PM
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Quote:
Originally Posted by Frank Reiner View Post
Your reference to the PTFE (Teflon) bearings I'm assuming is to coating on the cupped thrust washers?

No mention of same in the manuals which I have.
The cupped washers in this differential are 100% plastic - no coating

I'll clean them up and take another picture but the one on the right in this picture is all plastic under the grotty oil



If the "other ones" don't have 100% plastic cupped washers could this be why the W201 differentials get noiser quicker than their predecessors?

I'll be ordering some new stuff anyway so I'll compare thicknesses.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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