The W201 differential refresh thread

[vstech]

Jaybob and I are tearing into his diff. ya want me to put his carnage in this thread with yours or start a new one?

[DeliveryValve]

Originally Posted by w123fanman

so as a general question related to the topic, I'm planning on switching the entire ABS from my parts car (93-190E 2.6) over to my car (87-190D) and was just wondering if the ABS sensor port is on the regular diff or did Mercedes make the housing different? I could switch out the diffs but the 2.6 diff is 3.07 instead of 2.65 as in the 190D 2.5 and I'm not sure if I want to mess with that.

There's a specific casting for the ABS sensor. If you want the ABS to work, use the diff with the correct sensor port.



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[DeliveryValve]

Originally Posted by vstech

Jaybob and I are tearing into his diff. ya want me to put his carnage in this thread with yours or start a new one?

I say add in the carnage!

Great pics BTW stretch!

[Stretch]

Originally Posted by DeliveryValve

There's a specific casting for the ABS sensor. If you want the ABS to work, use the diff with the correct sensor port.

X2

Originally Posted by DeliveryValve

I say add in the carnage!

Great pics BTW stretch!

X2

Yeah add 'em in John it might make me feel a bit better about my purchase after diff doctor layback40 says his piece!

[layback40]

Originally Posted by Stretch

X2



X2

Yeah add 'em in John it might make me feel a bit better about my purchase after diff doctor layback40 says his piece!

Your the only doctor here Stretch !!
With all your dis-assembly, we should talk of you as a surgeon.
Surgeon Stretch !!
That dull surface looks like an oil problem. Normally you get a polish mark showing the contact point on the tooth. In my limited experience, noise can occur when the contact point varies as you move around the crown wheel.
maybe other members have more experience with this.

[Stretch]

Originally Posted by layback40

...
That dull surface looks like an oil problem. Normally you get a polish mark showing the contact point on the tooth. In my limited experience, noise can occur when the contact point varies as you move around the crown wheel.
maybe other members have more experience with this.

Thanks for your input. That oil is a problem - I might take my other differential to bits to see if that can shed any light on the problem.

I've been reading through the FSM this morning trying to figure out a way in which this contact can be adjusted / corrected. I think I've got it sussed - it is surprisingly complicated for a system with such simple geometry...

...I'm gonna do some drawings to explain it.

[Stretch]

It is worth noting that although the position of the pinion and crown wheels is a three dimensional problem the adjustments in practical terms can only be made in two dimensions =>


If the holes for the axial bearings in the differential are not aligned properly then there's little we as mechanics can do to correct for this error. If the centre line of the axial shafts are not at the correct height with respect to the height of the centre line of the pinion then again we as mechanics can't really do anything about it.


You might want to let that sink in! (If you really want to understand what's going on and what could go wrong)




Adjustments are made to the positions of the pinion and the crown wheel by the use of shims.


Shims are placed in three areas in the differential (for the adjustment of the pinion and crown wheel)


The position of the pinion is adjusted by placing a shim behind the inner most tapered roller bearing cup.


The position of the crown wheel is adjusted by adding shims behind the axial tapered roller bearing cups. These shims are circlips!





The circlips are shims!




The position of the pinion is probably going to be relatively easy to measure and adjust. The position of the crown wheel, however, is complicated by the pre-load of the axial bearings.


Bearings need to have a pre-load to stop them from sloshing about within the differential case. Sloshy bearings = noise {because there will be uneven contact between crown wheel and pinion}


At no expense spared here's a scanned in sketch of what is going on.





The position of the pinion with respect to the centre of the crown wheel is distance “x”


The position of the crown wheel with respect to the centre of the crown wheel is distance “y”


Think of the differential case as a great big C clamp. By stretching the C clamp within its elastic limits you can essentially use the springiness of the clamp as a way of pre-loading the axial bearings => you make it bigger than it is – you stick the bearings in there and release the pressure. It is a bit like making an interference fit – you stuff something slightly larger into a slightly smaller hole.


The problem is – and here's where you move from the realms of theory into the realms of practice – the differential case isn't a beautiful uniform homogeneous lump of metal. It is a roughly cast bell shaped thing with holes drilled in it. This means that when you stretch the opening (to get your pre-load for the bearings) one side of the case (y1) might not move as far as the other side of the case (y2).


This is a total bugger when you are trying to set your distance “y”...


...to be continued.

[layback40]

Hey Stretch, You should get your hands on a manual that describes how to set up a crown wheel & pinion. It will show the polish (ware marks) I speak of.
You are correct about the 2 direction adjustment.
The pinion location (how far back it is) is critical. The crown wheel can then be moved sideways to give the correct backlash. If this is not done correct the crown wheel & pinion will not mesh properly as its hypoid gears.
You should also have a close look at the spider gears. You will probably need to re-shim them.
Best just play with diffs one at a time.
Crown wheels & pinions are put together as matched pairs.

[Stretch]

Two sources of information here (in handy pdf format too)

http://www.geartechnology.com/issues/0611x/hypoid.pdf

Best one

http://fland.re:4444/Books/Engineering/Standard%20Handbook%20of%20Machine%20Design/69584_34a.pdf

[JB3]

question-
in the disassembled pic, I didn't notice any kind of crush collar that would be typical of US type rear ends on the pinion shaft. Does this mercedes diff not have something like that? It uses shims only?

[vstech]

Originally Posted by JB3

question-
in the disassembled pic, I didn't notice any kind of crush collar that would be typical of US type rear ends on the pinion shaft. Does this mercedes diff not have something like that? It uses shims only?

I've been researching this very thing...
the EPC calls it a spacer sleeve.
it's a crush washer that sits between the ABS reluctor and the outer bearing face. I THINK it's the spacer he has closest to the drive shaft end of the pinion in his tear out pic... however, in that location, it would not serve the same function as the US equivalent... so it looks like the MB diffs handle preload differently...

[Stretch]

I think it might be in this picture



It was on the input / pinion shaft

Here's a Russian EPC screenshot

[Stretch]

I've been investigating the cost of bearing removal and installation tools.

I've found that the standard sets that come in blow molded red plastic cases - that are usually multi-coloured in 1990s anodized aluminium colours are of no use what so ever. Even the top notch super expensive bearing removal kits don't seem to have the correct sizes for the bearings in this differential.

So today I gave it a go with a bit of South American bought from a garden centre hardwood...



I didn't think it would work. For the outer pinion bearing race you need a diameter of about 45mm to be able to push the race out of the differential casing.

I used a deep 30mm socket and some wood to support the underside of the differential (reaction side) and my hydraulic press. The gauge read nearly 2 tons before the bearing cup shifted.

The wooden plug barely has any marks on it. I could use it again!



(Well OK there's evidence of a slight depression around the circumference but this is a damn sight cheaper than the Mercedes special tool at 130 euros <= and that's just the attachment for the gucci bearing attachment)

Here's why it needed to come out



(Holy chunks Batman)

Whilst I'm not too happy about the next step of removing the inner bearing race from the differential with a hammer and punch this can be done with care.



Try and tap around the circumference of the bearing cup in a diametrically opposite way. Stop after a few taps to make sure that the bearing cup is coming out of the casing as straight as possible.

If you don't have a proper bearing extractor that splits, compresses and expands then there's no other way that I can think of to remove this cup. You can't get a "conventional plug of wood" in there because the diameter of the outer pinion bearing cup is much smaller than the inner bearing cup.



Don't loose that inner shim!

[Stretch]

Please note these are only good for my differential => I don't know for sure they'll fit yours - use this knowledge with caution!

Outer axial seals A 020 997 20 47 need two of them

Pinion seal A 023 997 90 47 need one of them

Outer pinion bearing A 001 980 61 02 64 need one of them - SKF equivalent number is M84510 / 2 / QCL7C (number printed on bearing cup)

Inner pinion bearing - 001 981 69 05 (about 35 euros) - FAG KHM 88610 <= This looks like a difficult bearing to find I'll let you know how I get on.

Axial taper roller bearings 1249800102 (about 21 euros)

{Oh and it looks like the crush washer spacer is NLA at the dealer! I have to check about that next week as it didn't arrive with the rest of the presents as expected}

[Stretch]

Someone else has recently asked about special tools here =>

http://www.peachparts.com/shopforum/mercedes-benz-tools-reference-library/345189-transmission-differential-rebuild-tools.html

In the spirit of helping out I've made a few screen shots that may as well be added here too. This shows what you are meant to have available to do the job properly...

...all of this information is currently available for free via www.startekinfo.com where you can get to see a copy of the W201 FSM