Here is a video to get an idea of how to check the preload with an inch pound torque wrench before removing the flange. Forward video to about 2:08 minutes for the procedure. Setting pinion bearing preload on the Ford 8.8" axle - YouTube
After installing the new flange tighten a new nut down to the same preload spec and strike it in place.


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__________________
1983 123.133 California
- GreaseCar Veg System

Hello.
I removed the diff from my 240d and removed the double hex nut without measuring anything. I also discarded the old nut.
I took advice from a mechanic friend who claimed that changing the rear seal was no big deal. He didn't mention measuring anything. He also admitted to using an impact gun. My bad and will never listen to him again before checking the FSM.
Now i don't have any way of going back to the original preload.
What should the friction torque required to turn the input shaft be?
Diff is without axles and lying on a workbench.
I know this thread is old.
Please help

The first thing to note is that there is a separate chapter in the FSM for just replacing the pinion seal and not having the rest of the differential in pieces and having it fitted to the car. In this case chapter you want is 35-530.

You can access this via www.startekinfo.com for free.

(This can be an awkward site to get working on some modern computers though - do a search for FSM + startek and you'll see loads of tips and tricks)

You are meant to measure the friction first and then when you put it all back together again you need to tighten it so it is back at that friction...

...but...

...this won't work for you now. So you should ideally be following the procedure for the whole revision => chapter 35-550

To do the job properly you should remove the crown wheel and differential assembly from the casing.

You tighten the pinion shaft nut so that you get a friction of 50 to 100 Ncm on a used bearing.

I'm guessing you don't really want to remove the crown wheel and the guts from the differential. (With these parts still in there you will have additional friction!!!) If I were you I'd tighten the output shaft nut to the middle of that range and then check the contact patch on the crown wheel with engineers blue.

I just so happen to be doing this job to my W201 differential today and I'm about to upload information in this thread =>

The W201 differential refresh thread

This thread (will / is about to) show you how to measure the friction and how to assess the contact patch of the pinion and crown wheel gears.

By visually inspecting the contact patch with engineers blue you are checking that you have the correct pinion shaft friction - because all you are doing is making sure that the position if the pinion is in the right place for the crown wheel...

...the friction method is just the way the FSM tells you to do the job - but the point is the contact patch position.

__________________
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!

@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.