Pinion Seal Replacement - How to determine Friction Load
 

I'd like to replace the rear pinion seal on my 87 300E. The manual speaks of determining the friction load. Does anyone know how this is determined?

Thanks,

Jim

An inch-pound torque wrench is used to measure the turning resistance of the pinion.

If you do not have the tools for measure, you can index mark the pinion flange nut so it goes back to the original position. That usually gets you back to where it was before, but not a true torque spec procedure.

This is the way I do it.
And I have an inch-pound torque wrench.

Me Too..

I only use the torque pre-load procedure if I change a pinion bearing.
I have one of those old Snap-On Torque-O-Meter from the Navy...kinda cool tool.

I have a Differential out of a W126 that Iam going to install in my 85 300D. I need to use the flange off the 300D and install on the W126 Diff.

The 123 has a smaller flex disc than the 126.

I purchased a new pinion shaft nut and oil seal. thought this is a good time to replace it.

I bought a new nut figuring using the old nut it wouldn`t stake in properly and might loosen up.
So how do I get the proper torque with the new nut?

also how would I use the inch pound to determine the torque preload. I have never done this before. splain it to me :rolleyes:. Iam a dummy in this dept.

I read another thread where the guy said the nut is a little more that finger tight. something like 0.75 in lb.

Charlie

Changing the pinion flange takes the easy way off the table since it's likely not the same height as the original. Use the torque wrench to measure the turning torque before you dis-assemble. When all is back together, tighten the pinion nut in steps until the initial turning torque is attained. A little more turning torque is OK.

Thank you for the reply.
I have one more question. do I unstake the nut first? or is that possible?

It would take a lot of torque to over come the staked part.

I also read to use an impact gun to remove the nut, or break it free.

I under stand torqueing it back on to get the proper tightness.

Charlie

<<I under stand torqueing it back on to get the proper tightness.

>>

Are you sure ?? That is tightening torque on the nut..and that only effects the turning torque of the pinion shaft.
One is very high Ft/lbs and the other is very small In/lbs.
It is the in/lbs force required to rotate the shaft [ bearing load] that determines how many ft/lbs you torque/tighen the nut...not the other way around...... the final measure is always the rotational in/lbs..and you use small increments on the ft/lbs b/c you do not want to excede the bearing in/lb loading spec b/c you can not take it back.

I just reread post#7 "use the torque wrench to measure the turning torque before you dis-assemble"

so I put the in lb wrench on the pinion nut, pull down on the wrench, and see what the reading on the wrench is to move or turn the shaft?

then when I reassemble the unit, I tighten the nut in small increments, check what it takes to turn the shaft with the inch lb wrench. add more as necessary to achieve the final number I startd with, w/o going past where I started.

now I have the Differential sitting on the bench, that would give me a different reading compared to it being installed in the vehicle with the axles in place. am I right with this thought? I then would have two different readings.

Charlie

The torque wrench readings will be valid if the task is started and completed with the rear in place, or if the task is started and completed with the rear on the bench.

CHAS H, you use a inch lb torque wrench. which type? clicker, digital, beam.

I apprciate the information given here, the muddy waters are clearing up:).

Charlie

<so I put the in lb wrench on the pinion nut, pull down on the wrench, and see what the reading on the wrench is to move or turn the shaft?>>

Yes..what you are measuring is the force it takes to turn the shaft..this is the friction of the bearing loading. That has a spec so that the pinion does not move lateraly when power from the engine is applied.
An easy way to invision this is a simple/generic front wheel bearing adjustment...as you tighten the WB nut , the wheel gets harder to hand turn..that is bearing load. Too much and you burn up the bearing, too little and you have a loose wheel.

So, if you measure the needed force to turn/rotate the pinion before dis-assembly, you know where you have to go when you put it back together. It is the final in/lb reading you are concerned with..regardless of what it takes, be it 125 ft.lbs or 165 ft/lbs , on the pinion nut to get there ,it takes what it takes. If you just used a set torque in ft/lbs on the nut, you would have no way of converting that into bearing load , as every case would be different.. That is why CH said Small Increments as you approach the correct in/lb loading spec. So you tighten the nut and then take a reading each time until you get the proper in/lb reading. There are factory specs for this if you do not want to use the original that you had before dis-assembly.
The problem can arrise if one where to go to far b/c you can not loosen back..that is the trick.
And that is why most guys just index the pinion nut and put it back where it was originally..the problem with that is you don't know if a guy was in ther before you at some time, but if the diff has been fine except for the seal, it is a good guess that all is OK.

thank you Arther for the fast reply.

I see you use a Snap-on Torque o meter wrench.

I have an old Sears beam type I bought years ago for an old Toyota head project, about 1974.
And I have a Sears Digitorque 250 ft lb.

since I will need an inch lb wrench, which I should have anyway, which one should I purchase for this project?

seem like some type of digital gauge, as I pull down I could see the # add up.

charlie

Yes

You want the lowest one you can find as that torque is usually 15-30 in/lbs....and a dial is very nice b/c you can see it creaping up there as you add torque.

Some guys use those 1/4/drive torque screwdrivers..they work great and are cheap...you can preset them cuz they have a clicker.

As CH said, you can go a little more on the in/lb reading b/c you have bearings with normal wear on them, so a little extra won't hurt any...but not much..1-2 in/lbs.
Many guys that use the index mark procedure will go a hair past the index knowing there is wear in the diff and that will tighten them up a bit,but caution is the name of the game here...which is why I always go get a final in/lb reading before putting driveshaft back on..then you know for sure.

Don't guess on differentail bearing loads ..I have seen too many in the dumpster b/c of foolish nut tightening w/o regards to load.

An added Note **

There is also a procedure where you wind a string on the pinion and pull the string with a scale [ like a light fish scale] ..that tells you the required force to rotate the shaft and you then just duplicate it when you re-assemble.
That trick is actually in the Benz Book for vintage cars , but most likely from when wrenches were not so available to the adverage Joe...get a in/lb wrench capable of low reading and do it right ..........

This is like doing brain surgery, very precise movements.:)

I planned on this project this week, see how it goes along with the Honey-do-list :D.

I`ll do a follow up how we finish up.


Arther< do you need another one of those 2 wire sensors like I sent you last yr? found another one.

Charlie

<Arther< do you need another one of those 2 wire sensors like I sent you last yr? found another one.

>

I knew/thought that was you ..... Thanks Again.

That was very good of you and I am happy to report that the one you sent worked to SPEC !!!! Yeah !!!

I still owe ya on that one.

Keep the other as there are always guys looking for them..they are expensive, too.
Ever see any more of those MFI engines , pull the injectors..they are getting rare as hell too...all that MFI stuff ..we used to see them everwhere , but not anymore...

[quote=Arthur Dalton;1972653]
Don't guess on differentail bearing loads ..I have seen too many in the dumpster b/c of foolish nut tightening w/o regards to load.
[quote]

I have seen failures due to tightening the pinion nut with an impact wrench.

<I have seen failures due to tightening the pinion nut with an impact wrench. >

Yeah..they want them " Goodentite"

I have seen only two on those old cars in the three PNP we have within 40 miles of here this past yr. at least with that engine. they are crushing them as fast as they can. :mad:

last I looked that sensor was $150.00 I think :eek:.

Charlie

<<last I looked that sensor was $150.00 I think .
>>

Yeah, which is why I was using a cabin toggle switch instead.........until you came to my rescue..........:)
Now I have Both.

Thanks all for the great comments. You really did a great job of explaining how to set the proper load on the bearing. I really appreciate all the thoughts.

Jim

pinion nut removal
 

Hello,

I'm in the process of replacing my seal.

However, measuring the axle load is confusing. I can turn the whole assembly with my hand, and doesn't register on my torque wrench either its so easy.

Whats the scoop, any input would be appreciated?

My Mercedes book tells me that the tightnening of the nut should be at least 180nM [133ft/lbs] over and above the torque to turn the wheels.

In another note anybody tried to get this &$#@*& nut off its incredibly tight. I have impact wrench but I'm hesitant to use it because of the possible damage to the axle and its bearings.

Gavinbr:rolleyes:

I've heard from several sources that impact type driven sockets should NEVER be used on a pinion nut.

For those of you that want to use the FSM procedures please note that according to that document the force required to move the pinion should be measured with the rear brake pads removed AND the rear suspension at normal ride height.

You need a very small torque wrench, typical values for turning torque are only 3-5 inch/pounds.

I have a small "beam style" wrench that measures 0-12 inch pounds, works great.

rear pinion nut removal and installation
 

Arthur,

So lets assume you have measured the torque as 12 inch/lbs, now what?

How do you put it back? This is terribly confusing!

According to my mercedes manual [Offcial Mercedes manual] is says tighten to 180Nm. If that can't be attained a new crush washer is required?

Sooo, why not just crank it to that number? Or, Are you saying that on the way to tightening the nut to 180 Nm, it shouldn't take more then the 12 inch/lbs to turn the pinion, the original example measurement. In other words, if after tightening to 180Nm the inch/lb reading now shows 25 inch/lbs to turn the axle, you tightened to much? Does that make sense?
I'm probably repeating what you have all ready said.

If I can get it off, nobody has given me any suggestions how. My nut is easy to put back where it was before because, the end of the nut is flush with the small protuding pinion shaft sticking out. Some people have said count the number of threads to put back, mine has no threads showing.

In an other note, if you decide to put new nut back on, guess what, Mercedes don't have the original style, the have gone to a "splined" nut versus the four prong style. Thats another tool you have to purchase. I purchased a four prong tool that's readily available on the internet. I broke the 1st one trying to get the @#$%^ thing off.

What about the impact wrench for removal???

Whats the scoop here.

Gavinbr:D

rear pinion nut removal and installation
 

This a note for those doing the rear pinion nut removal and installation.....

I finally got my holding nut off my 300D Euro.

I used a pinion shaft nut remover socket [special order] to remove it.
Don't buy the cheap one from "JTC tools" #1615 this broke the first go down.

I used a three foot bar on my socket it was sooooo, tight.
You will need to have somebody hold the socket in place while this accomplished.

I then torqued up to 180NM and or where I had marked before removal to get the correct loading.

Brian

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.


.

typical friction torque with diff on bench
 

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 =>

http://www.peachparts.com/shopforum/diesel-discussion/344307-w201-differential-refresh-thread.html

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.

@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 =>

http://www.peachparts.com/shopforum/diesel-discussion/303379-what-feeling-will-properly-adjusted-w123-w116-w126-power-steering-box.html

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 =>

http://www.peachparts.com/shopforum/...own-wheel1.jpg

(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)

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.

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...

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.

Awesome video:
Differential Ring and Pinion Gear Setup - YouTube

Good video but it does gone on

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.

Thank you for the reply. It is much appreciated. Your responses sparked further items of inquiry.

Can the existing 4-sided slotted pinion nut be reused? If using the same nut, at least I would be able to mark the position and compare the old position with the new one for an extra level of certainty with the torquing procedure. I've read of people grinding down a socket to make their own 4-slot flange nut.

What is the staking (peening) you are refering to? I went though a Google image search and came up with this possibility,
Attachment 123668
taken from http://www.gearinstalls.com/charles/charles12.jpg

Is this what you are refering to? I do not recall there being a flat edge on my pinion output shaft. I also do not recall there being any of this type of staking on my slotted nut. Do you have a photo of what you are refering to grind off? I am not sure how keep I would be to do grinding inside the small opening of the yoke orifice.

You mentioned to tap with a hammer on the pinion nut [in the direction of untorquing] to remove it. With these nuts secured with >180 nm of torque, will tapping the nut, which is inside the yoke orifice and the striking bar will be at a disadvantaged angle, always have sufficient impulse force to remove it?

If I have the proper 4-sided slot socket, do I need to bother with any of this? I beleive I have located the proper socket for $56 USD.

Once the pinion nut is removed, do I need some kind of puller as noted in the FSM to remove the yoke?

Oh bugger!

Well not really because staking or peening damages the nut - this is a method of physically locking the nut in place.

Yep people with time on their hands sometimes like to make tools!

Here's a picture

http://www.peachparts.com/shopforum/...-shaft-nut.jpg

(Taken from this thread http://www.peachparts.com/shopforum/diesel-discussion/304903-722-118-automatic-transmission-rebuild-monster-diy-3.html)

The method of removing the nut is also given here =>

http://www.peachparts.com/shopforum/2787565-post9.html

(This link goes to post#9)

Well yes you might need a bit of persistence!

If you want the tool then that's quite a low price. The dealer will sell you one for about 150 USD +...

...make sure you get the right one - there are several variations on the same theme including the rear axle wheel bearing version (now that one is worth getting in my opinion because the rear wheel bearing kits are still supplied with 4 slot nuts)

To remove the yoke I did this

http://www.peachparts.com/shopforum/...input-yoke.jpg

(Taken from this thread => http://www.peachparts.com/shopforum/diesel-discussion/344307-w201-differential-refresh-thread.html)

Stretch, thank you for your replies.

I have determined that I can reuse my 4-slot pinion nut one more time. There are two possible locations to stake the nut. Only one of them was used. The other location is 180 degrees away from the current staking position. That is to say, the shaft have two notches on it 180 degrees apart.

I have also decided to postpone this work for several reasons. Topping this list is money. I would need/want to buy a 3-jaw puller, a in-lbs meter, the flange nut socket, and other unforeseen items. Next is that I am not sure if all the grease splatter, which is on the the chassis, e-brake cables, etc. is due to the grease in the driveline centering sleeve (the rubber was bad upon removal), or if the grease is indeed originating from the pinion seal. My 240D is 35 years old, perhaps the quantity of grease is normal for this age vehicle? Perhaps the leak is slow enough not to be an issue. I will monitor the condition and check the fluid level in the diff. I need to get this vehicle back on the road so I can work on my Jeep's very leaky axle seals.

You could indeed peen or stake the other side and in a way it seems like you are saving money. You would, however, have to buy a tool (and say you have found the right one for what was it 50 something USD) instead of a 12 point nut that will cost less than 5 USD (and perhaps a deep 12 point socket for it for say 25 USD)...

...if money is tight I encourage you to look at the whole cost!

There is also the correct slotted socket on eBay for $25. I think it would be tricky to hammer the nut out while the diff. is in the vehicle on jack stands. If I do this job in the future, I'd want to use the proper socket.