107 LSD swap

[jbp]

Hi All
I have a 1976 450SLC that I have been driving and working on restoring/refurbishing for 20+ years of ownership.
I may have an opportunity to acquire a 450SLC LSD differential.

My query relates to the possibility of swapping in an acceptable ratio LSD in place of the current open diff (which has been rebuilt when the rear suspension was rebuilt many years ago) which is a standard 3.06 ratio diff.

Can anyone assist with advising what the case part number might be for the LSD type diff for 1976/77 W107?

Maybe it is the same as the non-LSD if it uses/shares the same case?
In which case it should be a direct swap using all the existing mounts and driveshaft components?

If not can the LSD centre carrier be removed from the LSD diff, serviced and installed in the current diff I have?
The advantage being the major gears can be retained and final ratio remains as is, and therefore speedo reading will remain unaltered and correct.

Also wondering whether there was a choice of LSD ratios, or whether all W107 LSD for period were only offered in a specific ratio?

Finally, I have been told that a 500SEC LSD will fit in the W107. I have my doubts??
However the LSD internals just might be common and be able to be swapped in? Anyone know?

The following are the part numbers I found in raised letters/numbers on my differential;
Diff case = 116 351 04 01, (note no "R" prefix)
Cover = R116 351 06 08
Stamped lower left rear diff case = 104900 3.06, which I assume is something to do with the gears in the differential case, with 3.06 being the diff ratio.

Thanks in advance.
John

[AMG]

There are a number of quite detailed threads regarding this. I suggest you use the search function and check them out.

viewtopic.php?f=20&t=19694

viewtopic.php?f=10&t=10086 for starters.

[jbp]

Thanks Joe
I had read those and a number of other posts in other forums and on line generally.

To be honest I was having some trouble following some of the discussion, and what the conclusions actually were regarding what if any diffs could be swapped in with no other reconfiguration, and/or whether the LSD internal carriers could be swapped in if the case was retained?
At one point it appeared to me that it was suggested that a 126 LSD carrier could be bolted in. But again I was not confident that this was agreed by all contributors.
I will read them again.... slowly.
Ideally it would be very helpful to hear from someone who might have actually done or tried this?
cheers
John

[CraigB]

1985, gen2 W126 changes slightly but prior to that anything should bolt in. LSD though is going to be rarer to find of course but more common for 500SEC you mentioned. Only problem is they are most often 2.24 that is a very tall ratio but some 380sec can be 3.27 i think (i have one). Some 450sel might have 3.07 like yours, early 350slc something like 3.46 but rare - W116 6.9 i think 2.65.

When you did your searching you might have seen detail discussions about what gears fit what - you may be able to pick up a 2.24 and fit your 3.07 gears to it.

Quick summary anyway that might help tie things together - I often have trouble with searches even when i know i have seen a post!

[CraigB]

And where are you located? Always makes it easier if its with your name - I can show you examples if in Adelaide.

[jbp]

Thanks Craig
I am in Sydney so a long way from Adelaide unfortunately.
I have just revised my profile and it now shows Sydney.
I set it up so long ago now, I don't recall even seeing Location as an optional field.

I have been offered what I have been told is a 500SEC LSD. I don't know what year or series.
I know it is a LSD as it has the tag noting the requirement for special oil.

My current diff is 3.06 ratio.
I was hoping that if a 107 LSD could not be found with the required ratio, and then directly swapped in. I realise this is a long shot.
The alternative was that if I could confirm the 126 LSD carrier could be installed, then I would see if I could use my existing gears and therefore retain the 3.06 final drive ratio.
Not sure if this is wishful thinking or not.

John

[CraigB]

that sounds good - I am sure one of the diff posts on here shows you the clear difference gen1-2 - a 500SEC can be either but gen 1s being wrecked i would say is more common. Where that tag is, if you scrape off the flat bits, facing to back of car in the main case - it has the ratio stamped there. It is complicated but all your answers are in the gen 1/2 link Joe gave you. I would say just make sure from that you have all the bits you need unless you want to run the supertall ratio. Also reminded me that just because it is a secondhand lsd, doesn't mean it works and hard to tell out of the car. If it is worn parts are expensive. Having said that, every LSD i have in a working car will spin both wheels, including my first 560 that had rubber lining the inners of both rear guards from the 'child' that owned it before me, so i reckon they are pretty tough. I mainly say that because if the seller wants a million bucks for it, i would bear in mind that there is no guarantee it will work when fitted.

[jbp]

Hi Craig
Yes I will read those posts again and see if I can find the relevant bits and confirm if there were any definite conclusions.
Also see if I can find the info on how to tell the difference between a series 1 and 2 126 LSD.
From what you suggest it sounds like I could use the series 1 but not the series 2 LSD internals?

Yes I was aware of the potential for the Diff to be somewhat of a lemon.
I had actually rung a Diff shop (they rebuilt my brother alfa spyder ZF LSD) and tried to get some indication of potential issues and costs. Didn't really achieve anything alonmg those lines so far.

I guess the first test will be to try and rotate one of the splined output drive shaft sockets, whilst holding the input drive shaft and see if the opposite output shaft rotates in the same direction. If this is possible at keast then I might know if the diff is free internally and a LSD diff?

[AMG]

The main thing to be aware of is the housing, and the ratio.

Don't muck around and try to put bits inside. simply replace as a unit.

the LSD diffs have a tag on the lower right hand side of the rear hat.

You really want to maintain the exact same ratio. If you don't, your speedo will be out by a considerable amount. replacement speedo's are not easily found for 107's and certainly not in the 500SEC w126 ratio.

For each ratio, there is a speedo head to match for the specific model the diff was fitted to. So if the model vehicle did notcome with that ratio, then you will not find a matching speedo.

That's the first bit.

The second bit are CW&P offsets from the carrier. This is the main point of discussion in the previously mentioned threads. It is NOT straightforward. This is why I suggested you only swap like for like. i.e. swap the complete unit for a complete LSD unit in the same ratio.

Don't try stuffing gen 2 internals into a gen 1 housing. For one, you will never ever get the damn thing quiet, it will have period noises that you simply cannot lap out. Secondly, the preload and pinion offset is set ex-factory in a huge jig. This is not able to be replicated, no diff shops have the tool here. I've looked high and low for them, but it seems only MB have them. They were used to set the pinion and were accurate to 0.01mm most people can't read a micrometer reliably to that accuracy.

Physically, Gen 1 diffs have front tags which are short and contain studs. they bolt into the subframe front plate. Gen 2 diffs have a much wider front tags with no studs and a rear hat containing an offset bush which mounts to the subframe.

Your diff and subframe is the gen 1 type. You should be able to find an LSD from a w116 or R/C107 with the correct ratio. This is where I would focus my efforts on.

I would not bother with 126's, as they had 4 speed auto's, and the likelihood of finding a 3.06 with LSD in a large 210mm housing is not going to be easy. Most of the large housings were 2.82 and 2.47 with the rare 2.28 being way too high for your application.

So it's not that you can't fit an LSD carrier from a gen 2 - the problem is you're going to be kicked in the balls over the price on the LSD clutches, the diff will never be dead quiet as they were ex-factory and you'll probably have better luck finding a 450sel parts car or a 350se or something which has the ratio you need and in LSD.

Be aware, that you may find it cheaper to purchase a complete vehicle as a parts car just for a diff. I know people who have done this. So if it comes to that, make sure you offload some bits n pieces as well as keep the engine bay electrical parts for your 107 d-jet.

cheers,
Joe

[CraigB]

I got curious and tried to get my head around it.....unsuccessfully.... but if you go to the gen1/2 thread and go to Julians post 31/5/2015 and there is a clear diagram showing gen1 gen2. I totally agree re trying to find w116/107 450 3.07, but I have never seen one for sale and i had always thought they were pretty rare. I bought the 3.07 i have from someone with a 6.9 and couldn't find one so he had 3.07 gears fitted to replace his 2.65 gears and although i haven't run it i trust that it is quiet. JG might have even arranged for the rebuild on the diff. Might have been lucky too of course. So depending on how much of a rush you are in, i would chase the 3.07 but the other question I would look at is can you fit 3.07 gears to a 2.24. And you need to look at that diagram and see if this SEC diff is gen 1 - better than even chance i would say that it is.

But all diff rebuilders must have the same training - never help a customer try and work out the possible costs!

[AMG]

But all diff rebuilders must have the same training - never help a customer try and work out the possible costs!

Haha, you have spoken to the same people I have over the years. :dance: :occasion5:

Bottom line, pretty simple.
New bearings for carrier, new pinion bearings.
New Shims, and crush washer. (the most important parts to keep it quiet)

for an LSD centre, the steel shims in theory *should* be OK and easily rubbed with some 180W&D and solvent, should get a good surface back.

The Clutch frictions however, are just absurd. To get replacements, you need genuine MB parts, no other friction material seems to work. I did this with my 560 and regret every second of it, it's worse than the used original parts.

for the frictions, you need to ensure that when they are finally packed in, that they are tighter than a fishes.... seriously.
I know the manual says this and that about preload and all the other BS. You want it TIGHT. as soon as the diff is filled and the frictions take up the LSD gear oil, they will slip some more.
At this stage I'll also mention it's really important to use an LSD oil that meets the MB specification. Stuff like Castrol LSX90 doesn't. So don't use it. Also, avoid stuff like Redline oils 'Shockproof' series of oils. They have friction modifiers in them which separate out and in some vehicle applications (like subaru) the oil has been linked to the failure of components (blocking oil galleries with the separating modifiers)

So, stick to genuine or a fluid that meets MB spec. Fuchs make it, as do Elf, and Neo Synthetic oils in the US also make a 140wt with the viscosity of a 75, and this is very good stuff, but horrendously expensive. (but it's synthetic, and you won't need to replace it for another 2-300,000km)

Personally, after all of the stuffing around, I ended up fitting a Quaife qdf5v to my spare 560 2.47 diff, and I haven't looked back. In the long run, it is the better solution, but not the cheapest one.

[jbp]

Thanks again Joe and Craig.
I do appreciate yout time, patience and knowledge.

I started this whole process with the idea of finding a 107 diff that was the correct ratio and LSD.
What I didn't know then, and was trying to find out was, if I could swap in one for the other without changing all sorts of other parts that are related, such as driveshafts....
It appears from what I have heard recently, and what you gentlemen have said here and in various other threads, is that it should be a direct swap. Thats good news.
This was the original Plan A and perhaps I should just stick to that.
I did get diverted along the way by diff technicians talking about converting my existing rebuilt diff by ......???
Then I heard (separately to this forum) that 126 LSD internals would fit in a 107 open diff......

The reason I liked Plan A in the first instance is that as I had completely stripped and repainted/refurbished/rebuilt the rear suspension, including the diff many years ago, I preferred to retain as many rebuilt components as possible.
I understood swapping in a new diff is not a particulary difficult job, and it seemed to make sense to buy a 107 3.06 LSD diff (I know .... not easy), have it rebuilt and simply swap it in whenever I have the opportunity. And then keep my existing 3.06 open diff.

Again thanks for your assistance. I have more phone calls to make.
I will certainly let you know how I go...
Cheers
John

PS
If I can work out how to post photos I will do so of my current rear suspension.

PPS
Yes Craig. I don't think I got a single direct answer or estimate from the alledged diff experts.

[jbp]

By the way Craig and Joe
I did read again, and reread, and reread the two threads last night.
I think.....I get it.
cheers
John.

[Greg in Oz]

Having owned a 350SLC with an open diff for 29 years and now a 500SLC with an LSD for 9 years, I recommend that you be sure you really want an LSD. Yes, they help get the power to the road but they also turn a very forgiving car into one that will quickly bite you. Being a bit aggressive with the right foot on a greasy road with an open diff will just see the unloaded wheel spin. Doing the same with the LSD will turn the car around and have you pointing to where you've just come from.

[CraigB]

I think the principle of what Greg is describing (if you didn't work it out already) is that in low traction conditions, the spinning wheel will have less grip in a sideways direction and if you are hooking into a corner and put your boot into it, even the non-lsd will tend to 'step out' a bit. But you still have one rear wheel that is hanging on and giving you that sideways traction. If both are spinning there is nothing hanging on at the rear with the sideways movement and in a heartbeat it will spin and it is slippery anyway and can get into all sorts of trouble. Also diffs can be set up different, or wear more, and some will bite and lock the two wheels together sooner and with less power going through them, and that will make it that much faster to spin you around and harder in the wet. I am recalling this from a mate also doing sprints in a 105 alfa with healthy power output. Mallala with lots of corners, if you get the power down sooner out of corners you are going to launch sooner, and so this mate had his LSD shimmed for plates to be tighter and lock in sooner (not all lsd are the same but this has the plates and the ramps on a pin where when under force it slides the ramp up the pin and therefore squashes the clutch plates together that lock the wheels together - tighter the plates, quicker it locks - i think the benz diff is same?) Anyway, he made exactly the same comment on a test run in adelaide hills in damp conditions - very quickly found himself pointing the wrong way.

How much power you are pumping out makes a lot of difference and of course there is a fair difference between the 350 and 500, weight difference too but balance better on 500 with alloy motor up front. Power wise in slippery condition and the 500 is going to be pushing that power through to lock the wheels quicker and make your response time that much quicker to be able to stop the spin. Also feeling it through you pedal and bum too. But when it is dry and you are going for a 'squirt', if you have good power, instead of one wheel spinning and losing that push out of the corner and having to back off, instead both wheels are putting the power done without spinning and you can really put the boot into it.

But it is a really good point to make and brings up that question about why you want it for all the effort - i did actually make that point in my original message but then my hand touched my mouse pad while typing and that tends to delete my message and i have to start again! Can't seem to desensitise this keypad and half the time i can't even turn it off- was told this ASUS was better than my old HP but i think it is crap! - I digress!

But it is a good thing to think about -if it is a cruiser etc you will hardly notice the difference but if like me and you are yet to grow up and cant help sink the welly on a windy road then the lsd can make it more fun...... in the dry!

[jbp]

Hi Greg and Craig.

As always, thanks for the comments.

My SLC is an english import with the higher compression 450 K Jet engine and no polution gear.
I have owned it for around 25 years and put well over 100K klms on it. It was my daily driver for a long period of time, and I have been rebuilding/restoring it for the whole time in varipous fits and starts.

As an aside, when I had the timing chain and guides replaced for the second time last year I noticed and appreciable increase in torque immediately available off idle with the result that I am now learning to be a little gentler with the throtttle application from a standstill.

As to experiences with LSDs. I have owned a variety of cars over many years. Many with an LSD such as an original VC Brock commodore, Alfa 105 ... and many without, such as a LJ Torana XU1, worked MG B. And all sorts in between from Lancia Fulvia Rallye GT to Forester GT and on it goes. I am sure most on this forum have had similar experiences.
And I have been guilty of driving cars and having the car swap ends in a blink of am eye. I have one very clear memeories of dioing it in the Brock commodore and in the MG B.
So I have certainly experienced (rather stupidly!!) what has been described. And to be clear, if I wanted the LSD as some sort of 'go faster' option I would have added it 20+ years ago.

Greg your point is a good one but only tells part of the story I think.
I live in Sydney's East and here have some very old, steep and poorly cambered roads. There are several bends and intersections I use on a semi regular basis, where one of the rear wheel loses traction due to the severe twist in the raod, and an LSD would assist here I feel.
And Craig as you suggested, how the diff is set up may have some bearing on its lock up function (I am not sure to what extent the MB LSD can be adjusted for this lock up, if at all, but may find out soon?) as does the final diff ratio to a much lesser extent.

Also, whilst quite a few horses have no doubt escaped, the 450 engine still produces sufficient torque off the mark to spin an inside wheel if turning even on a dry road.
And in the wet, on even moderately greasy roads, I have to be exceeding careful not to lose traction.

So why an LSD now?
Especially as I have already rebuilt the entire rear (and front) suspension, including the diff, gearbox and driveline?
Really because it would be a simple "project" that would imo improve the safety and general driveability of the car, using a genuine factory option. No more complex than that.
I am in no hurry, and work still seems to demand much of my time, but if i could find the period correct 107 LSD in the correct ratio I would be interested in having it rebuilt and swapped into my SLC.
And the best part is, as it is a relatively simple job to do so, if it did not work out, I would simply swap it out and sell it, given there is probably a market for it even here in Australia, and re install my existing diff.

Hope that provides a little more background.

Cheers
John

[jbp]

Actually, on reflection, the XU1 may have also had an LSD?

[CraigB]

It sounds like you know where you are at. Its funny how we offer information on here, best intentions to help, but even if we preach to the converted it is still there for others to maybe pick up in a search. And you can just keep your eyes open for what you want and it is not hard to change a diff, especially if you build up an lsd complete with axles. then it is just a matter of detach tailshaft, 4 blots to subframe, bolt in middle of hub and drop it down. A bit more wiggling and swearing than that but not a hard swap.

[jbp]

Hey Craig
I still have a way to go and will gladly taks all the good advice I can get.
Interesting .... idea about taking the half shaft axles as well?
I had thought about taking the whole rear suspension but quickly discarded that idea as storage space is at a premium now as it is.
Taking the rear drive shafts is a good idea, although it does increse the cost by meaning CV joints and other refurbishing engineering work.
Probably insignificant in terms of the cost to rebuild the LSD and clutch packs (assuming they need to be replaced/refurbished)?

I did read in the MB workshop manual that one needs to be very careful dropping the diff with drive shafts attached as if the angle becomes too acute the drive shafts may be damaged?

I could not find a section in the workshop manual dealing with 107 024 LSD.
I did find a supplement for the 560 SL. but nothing for the 1970's W107 LSD.
If you could steer me in the right direction I would appreciate it?

Re the LSD, I am still looking and in no particular rush. If it doesn't happen so be it. I will not lose any sleep over it.
I am in the middle of replacing all my door and window seals and all associated clips and pins, as well as adjusting the window slides etc. Done the drivers side but the passenger side is going very slowly!!!

Then look at mounting the 390 mm Nardi timber wheel.
And then maybe putting tyres on the 16 x 8 Penta rims I had refurbished and have had sitting in the roof of my garage for many years now.
Although after refurbishing my 15 x 7" ATS Bundt style rims, and polishing the lip, I am thinking I might leave them on the car now??
Still plenty to do.

Cheers
John

[jbp]

A quick update as it has been a while ...
I purchased a LSD for my SLC last year, it also came out of an SLC as it so happens and the ratio matched.
I had it completely stripped and rebuilt using quite a few new parts.
I have yet to paint the rear cover.
If I get that done this weekend I hope to be installing it next week, in place of the refurbished standard differential currently in the car.

As many would know the Mercedes LSD gear oil is veryexpensive.
I was wondering if anyone on this forum has had any positive experiences with using other brands (Penrite, Castrol etc.) premium gear oil in these early LSDs?
Thanks

[Lance]

Many, many years ago when I used to race minis the cheap way to an LSD diff was to have a HQ LSD modified to fit the mini crown wheel. There was someone in Melbourne who did it. I had mine done and ran it in the car for some years. It was quite cheap to do. It does seem strange to fit such a large diff centre in to a small housing but it did work. I am not suggesting using a HQ diff, but surely it wouldn't be hard to modify a diff centre from some other car to fit the Merc diff. Just needs some investigation and design work.
And yes, the handling of a tight LSD in a front wheel drive car was interesting - lots of torque steer and power oversteer!

[AMG]

A quick update as it has been a while ...
I purchased a LSD for my SLC last year, it also came out of an SLC as it so happens and the ratio matched.
I had it completely stripped and rebuilt using quite a few new parts.
I have yet to paint the rear cover.
If I get that done this weekend I hope to be installing it next week, in place of the refurbished standard differential currently in the car.

As many would know the Mercedes LSD gear oil is veryexpensive.
I was wondering if anyone on this forum has had any positive experiences with using other brands (Penrite, Castrol etc.) premium gear oil in these early LSDs?
Thanks

You can run castrol LSX90 in it, but the genuine stuff is far superior and has much better friction modifiers.

There is a reason mercedes diffs last a long time - even when owners never ever change the oil.

[jbp]

Thanks Joe
I did originally intend to use the OE MB special LSD oil, as I usually prefer to use OE parts and follow original specifications when restoring or rebuilding.
However when I checked, the MB LSD special gear oil costs nearly $160 for 2 litres!!

And given the MB LSD special gear oil is undoubtedly made for MB by a separate specialist oil supplier, I thought 40 years later I could source a more advanced, perhaps fully synthetic, gear oil, that would exceed the 1970's nominated MB235.3 specification.
I imagined that someone, somewhere had been there before me, and had either good (or perhaps not so good) experiences with other suppliers premium gear oils in a rebuilt 1970's MB LSD.

I have spoken several times to both Castrol and Penrite, as well as the firm that rebuilt my LSD.
The options are many and varied it would seem.
I am currently looking at using Penrite Pro Gear 75W-90 (Full Syn.) which from memory meets MB235.7.

Open to any advice or suggestions at the moment.
Especially interested to hear from anybody who has had a good/bad experiences with this.
Cheers

[jbp]

UPDATE
For those that were following along and providing advice, thought I would bring some closure and update this thread.

I had the LSD rebuilt earlier this year and the case media blasted and repainted.
Two photos of LSD after rebuilding and before installation are below.
I elected to go with quite a few new parts when having the LSD rebuilt. The new parts included; replacement bearings; 8 Clutch plates; Pinion gears and spherical washers; Side seals; O ring carrier bearing seals and Pinion seal; Pinion lock nut and Crush tube.

I have recently had the refurbished LSD installed in the car.
Although I haven’t had an opportunity to drive the car much further than about 100 or so klms, I am happy with the result in the usual heavy traffic conditions in Sydney as well as the performance on the motorway at speed.
I carried out a basic test on the LSD after installation by simply accelerating from rest on a grassy road verge, and it appeared that both rear wheels drove the car forward and straight, with very little if any sideways movement.

The refurbished open diff, that I had rebuilt about 20K Klms ago is now sitting in a plastic tub, whilst I think about what to do with it.
I can’t see that I really need to keep it as a spare so may well be easier to simply put it up for sale.

Will post some photos of the LSD installed when I get a chance.

LSD2.png

LSD1.png