LSD80% VS LSD40% M220 "Factory"

[_gonbau]

All LSD’s in the early cars were 80% into the mid 70, then they were 40% thru 84 with multi plate diffs that could be adjusted. Then in 85 they became non adjustable 40%. If you didn’t like the locking value of an early diff you would adjust it, as there were 4 or 5 different adjustment settings. Don’t try to make a mountain out of a mole hill, it wasn’t that complicated. I did a 72 ST some years ago, it had 80% diff. The LSD option was not that common, mostly special order. The dealers I worked for never ordered them for cars they were flooring, thought they were dangerous.

I have just seen this response, and it does not answer my questions. We have observed that in 1972, different LSDs with 80% and 40% could be installed. Does this mean that the factory differentiated them when installing them in the vehicles in some way?


I don't think my question is difficult to understand. While I understand that this topic might be repetitive, in this post we have seen different opinions that have been clarified with documents.


It is known that LSDs were not common, and they were usually requested if the driver wanted better vehicle performance. From my perspective, LSDs could be dangerous. In the case of our vehicle, the second owner, who had an accident, may not have been accustomed to them, leading to the loss of control. I suppose that at that time, installing an LSD was an uncommon upgrade that would have drastically changed the vehicle's handling. However, I am still wondering how the installation of the LSDs was differentiated. These questions may never be answered.
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https://porschecarshistory.com/wp-co...r%20Morgan.pdf

[_gonbau]

Do all vehicles (in 1972) with a Limited Slip Differential come with the handwritten inscription "SP" on their build sheet? I've been quite insistent on this because it seems strange to me that the inscription would be on some vehicles with the M220 and not on others. This has made me doubt, as I've expressed before, the meaning of "SP" handwritten. I've also tried to find information on how the factory installed and NOTATED on the build sheet whether it was a 40% or 80% LSD, but I couldn't find an answer. The only thing I've been told is that "SP" stands for "Sperrdifferential," and my question is... why do we know this? Where does this clarification come from? And why is it emphasized on some vehicles and not on others? Why couldn't "SP" (for example) stand for "Sportausfuhrung"?
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I have raised these questions these days directly to the Porsche Archive.
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These questions were never answered by the Porsche archive

[_gonbau]

I keep trying to find documentary evidence indicating that 'sp' was the abbreviation for 'differential slip limits.' I've seen the image of the label in this post indicating 'SD' instead of 'SP,' so I'm asking again where this explanation comes from, stating that 'SP' is an abbreviation given by the German factory, an abbreviation in German 'I understand'... Is there any document that supports what you're indicating in this post?

[928cs]

You will find SP or SD, for SPerrDifferenzial.

I have also seen, "SPD. 40%" written on a 928 gearbox, of a very special type.

[_gonbau]

I have never seen the handwritten notation of "SD" but the explanation about the other vehicle is worth it I guess! That inscription that you mention... was it made by hand on the construction sheet or are you talking about some report that Porsche provided?

[928cs]

I have never seen the handwritten notation of "SD" but the explanation about the other vehicle is worth it I guess! That inscription that you mention... was it made by hand on the construction sheet or are you talking about some report that Porsche provided?

On the gearbox itself, with a pencil

[_gonbau]

Any news regarding this? Would the adjustment to 40 or 80 (u 60) be made by the sports department after manufacturing, and was an LSD always installed as standard? From my point of view, I doubt it, and if I'm right, there should be something on the sheet from the assembly/construction indicating an adjustment on the LSD. In some documents, we have seen the lock percentage mentioned as a feature in some Porsche letters, so it must be referenced somewhere. Is there any information on how the adjustments for different percentages were noted? For any year, especially in 1972?
https://www.early911sregistry.org/fo...3&d=1627303934
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Does anyone know the percentage of LSD that the vehicle equipped with M491 had? Did these vehicles have LSD220 to control so much engine power? It's understood that with higher engine power, especially on the circuit, which percentage would be more interesting?
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SPerrfaktor

[_gonbau]

Over time, I have been observing how the construction sheets were made. With their order, when performing all the pending tasks on that sheet. I observe SP written by hand again and the same question comes to mind.
Why?
At the end of the vehicle's construction, when the chassis has already been worked on, the engine has been mounted, and the transmission has also been installed. Why? After that moment, when the transmission and LSD M220 (which have numbering) have already been installed along with the transmission, is SP written by hand... and M220 is underlined?
Why, when there is no more work to be done on the vehicle (it has already passed through all departments, except "one"), is that handwritten note made as if to imply that it was written after the entire assembly process and the sheet was completed. Then, according to the forum theory that SP indicates spiderdifferential/LSD, why that note, at a final moment when the vehicle has already been built?
Why highlight M220 with a black line and add SP written by hand when all the work on the transmission and limited-slip differential has already been done?
That SP note, in my opinion, does not indicate spiderdifferential but SPerrfaktor.
I don't know to whom that handwritten SP note on the construction sheet belongs. Did these vehicles pass through the sports department? Is that note made in the factory or in other vehicles? For the year '72, in my opinion, it may have been done by the sports department except Z-programm 471+491 Completed in the same place where the vehicle is produced.
These are all theories that I have based on some construction sheets that I have found, like the one Huhgg showed some time ago.
From my understanding, that SP mark indicates an adjustment work on an already installed differential in the vehicle.... Nothing to remember or forget... Everything was written down and reflected, so I would like to clarify if when they told me there was a label that said SP, it was the image that showed where it said SD. And also, I would like to know where the theory that SP is Spidderdifferential comes from since I have seen that everyone, without exception, thinks the same. I would like to know what it is based on, apart from the writings on the same transmission box...
From my perspective, "SP" is a sports adjustment.
From my perspective, "SP" indicates a 40% adjustment and is the way to differentiate them on the construction sheet when adjusting, which is not the same as assembling.



https://pbase.com/archive_racing_por...0_0945_n126200

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From my perspective and with reference to the handwritten SP inscription, in Z-Antrag vehicles that include the M471+491 package, the SP handwritten note should not exist, as the entire process was done (I think) in the same place, where I also believe the LSD, which is part of the Antrag 471+491 package in the vehicles where it was installed, was adjusted.
Now, if this is the case for Z-Antrag vehicles concerning transmission and M220 adjustments, I would like to examine the sheets of the 21 clients from 1972 to see if this adjustment also exists in them.
or it was carried out somewhere other than where the M471+M491 vehicles were worked on.
and let all this be understood as uncertain information, because if not...
Does anyone know with which Sperrfaktor the 1972 vehicle 495 was delivered?

[gled49]

I did the gearbox in 495, no type number, stamped numbers only, 80% diff, special ratios and prototype style oil pump. I’ve never seen any early gearboxes with hand marking, that was later in the late 70’s & 80’s. As done with production numbers stamped in knee rail, the grease pencil markings on the dash were for quick reference. If you didn’t like the diff settings, I’m sure you would be referred to the service manuals for re-stacking the diff plates.

[_gonbau]

I thought the transmissions equipped with 220 had an stamped* inscription; perhaps these special vehicles do not. Is that what you're indicating? Is there any image in the forum of the oil pump or where it was mounted? Was the support provided by the transmission, or were there places on the chassis to fix it?
Regarding the percentage, I understand what you're saying; it was explained before. But when a vehicle (for example, M491) was to be factory-fitted with the percentage at 40%, how was that difference noted compared to the other M491s (like 495) with the percentage at 80%? I understand it's easy to adjust, but the question is about when the factory set it at 40% or 80%...or 60%...
When the employee installed the LSD, it's clear that it was always installed at 80%, right? Never at 40% from the factory? Was the LSD adjustment done by the sports department by any chance? Or could this LSD be adjusted on the assembly line? From my perspective, it was always set at 80% (standard) and then adjusted later. My theory is that this adjustment is noted as SP. But without more examples...
On another point, what would be the purpose of an LSD at 40%? Would it help to better control the engine's power? Would it make sense to install a 40% LSD on a 632XXX engine? Or would that percentage be excessive for that type of engine? The simple question is whether the 40% LSD was intended for the M491.
And thanks for your clear response.
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I found some documents that show LSD at 40% and SP notation so my theory or what was shown here in the last post. It's wrong!
Likewise, it still seems strange to me that notation by hand ONCE the transmission is already assembled.