@Stretch - I am following your 201 diff rebuild thread It does cover measuring friction on the drive pinion. I remember one of your threads about adjusting a steering box and a very clever wooden ruler type thing and weights
Would it be possible for you to measure friction with the crown wheel and differential assembly installed to get an idea on how much the friction increases from 50-100Ncm.
You are right about everything.
Without removing the crown wheel and differential assembly from the casing i will not be able to accurately measure friction load of the drive pinion.
It's hard to guess what the friction load should be when the crown wheel and differential assembly are installed. My guess would be certainly above 100Ncm since with the drive pinion alone it's 50-100Ncm.

The FSM chapter 35-530 says that minimum torque for the shaft nut should be 180Nm. This is the starting point for further adjustment.
Thanks to your suggestions I have decided to do it the following way:
-Torque the new pinion nut to 180Nm
-Measure friction on drive pinion nut
-Assess the contact patch of the pinion and crown wheel gears using engineer's blue

After that I will either be OK or will have to make adjustments.

35-530 does indeed say minimum of 180 Nm - and it will probably take that much to get the friction correct - but I wouldn't blindly just do that.

I think the measurement of shaft friction is indeed the best way - ignore the comment in 35-530 - the real point is the friction you end up with - which in turn is all about making sure the contact patch is in the right place (as well as it being tight enough for the bearings).

The method of using a balance bar is indeed the method to use if you don't have a fancy torque wrench that can measure various Ncm values.

Starts at post #8 in this thread =>

What a feeling it will be! A properly adjusted W123 / W116 / W126 power steering box

__________________
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!

On second thought
Will I be able to put engineer's blue on the pinion teeth with the diff fully assembled?

You won't be able to reach the pinion wheel but you apply it to the crown wheel after removing the back. Degreasing will be necessary. It will look like this =>



(I use too much engineers blue - apply it a bit more sparingly - the stuff I use needs a good quality hand cleaner to get it off of your hands)

__________________
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!

OK so latex gloves are a must
I see two possible methods.
1)
I will apply a very thin layer of blue to all crown teeth and do a full turn.
This way the areas on the crown where there is a change in color (to lighter?) are the ones that made contact with the pinion.
2)
I will apply a generous layer of blue to all crown teeth and do a full turn.
This way I will have all pinion teeth covered in blue.
Next step is to clean the crown wheel teeth while doing another full turn.
This way I will have marks on the crown wheel exactly where it made contact with the pinion.

You are best off coating all of the teeth - there is likely to be some uneven wear as it probably wasn't made absolutely perfectly in the first place. Take a look at the "average" contact position around the whole crown wheel and make your assessment / judgement from that.

__________________
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!

OK. 3 days from now i will have the diff at home and i will try what we discussed. @ Stretch - If you found the time to measure friction with entire diff assembly installed I would be very grateful.

I don't think that's going to help as the one I'm working on is for a W201 and there will be new wheel bearings as well as new bearings in the differential...

__________________
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!

Good point. If I could only remove the differential from the housing...
I would have to have two special tools - one for spreading and other for measuring spread so I can go back to zero spread after reinstallation.
How about heating the housing? Would that be enough to get the left and right axle outer bearing circlips out?

@Stretch - I see in your w201 diff thread you managed to get the differential assembly out without expanding the housing. I will try that.

That's the ticket - it pulls out nicely on the W123 differential as well (with worn bearings). You just need to be a little bit careful when putting the circlips back in because you should in principle be stretching the case - but it is a very small amount.

__________________
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!

Awesome video:
Differential Ring and Pinion Gear Setup - YouTube

Good video but it does gone on

__________________
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!

I have read the 10 most popular google-searchable threads on replacing the a Benz pinion seal and have a few questions which I could not find satisfactory answer to. I also read the FSM.

1) Where do I source the slotted flange nut socket (4 slots)? What size is the socket? i.e. 41 mm OD, 35 mm ID, 7 mm slot length, 8 cm tall socket?

2) I've read that the nut is "striked" in place. What does this mean and do you have a photo of this?

3) I read not to use an impact gun on the pinion nut. With the wheels off the ground, how are you holding the yoke steady and use a breaker bar to remove the nut? Which yoke holder are you using and where did you source it online? Seems like even if you had some kind of lever-arm based yoke holder, you'd be fighting with both of your arms wanting to go in different directions.

4) Is it acceptable to leave the rear wheels on the ground, car in gear, and e-brake enabled and use the resistance of the gears to hold the yoke stable while untorquing the pinion nut?

5) It has been mentioned that the in-lbs torquing screw drivers can be used to determine pinion bearing pre-load in the 0-30 ft-lbs range. Any drawbacks to this lower-cost alternative compared to the Snap-on style of in-lbs gauge?

Thanks a lot!

The slotted nut is no longer available to buy from Mercedes they have replaced it with a 12-point equivalent.

There seems little point in buying an expensive tool to remove a nut when you can grind off the "staking" and tap the slotted nut round with a hammer and punch.

People are talking about "staking" or peening. Is a photo of this really necessary? I can dig one out if you really really want me to...

I wedge something between the yoke and the casing of the the differential to do this job. I do not use an impact gun. Spending time removing the staking takes longer but you stand a better chance of not damaging stuff by force.

Some people say it is acceptable. I'm not so keen on that method. On the W201 differentials in particular you see lots of images of broken differential gears (not pinion or crown wheels the other smaller ones) due to too much force being applied - granted these are usually pictures because people have added turbos / driven like nutters but that seems to me to be a weak point in the W201 differential...

...also on a Mercedes limited slip differential this would probably help the demise of the friction material...

It is a question of calibration when you are comparing specifications with the FSM. For just putting the torque back to what it was before you removed the nut on the pinion shaft any repeatable method (whether you have a calibrated reading or not) is just fine.

There is a subtle difference between stiction and rolling friction - but my estimates are that they are pretty close to each other is an undamaged differential.

Replacing the pinion seal and putting back the pre-load is all about repeatability - getting the system back to where it was before.

__________________
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!