2800 CS differential or not?

[JFENG]

But are you saying that some side-loader differentials in the e9 cars have lsd but it’s not visible because there is no external reservoir and tube

AFAIK, none of the original E9 LSD's had the external vent/reservoir, except those modified by people like Alpina (who had an optional oil pump driven off the output flange to circulate to a cooler for racing). Some of the E9 LSD's may not have been marked with the "S" on the outside (or it wore off). Retrofitting the later vent and external reservoir from an E24 or E12 is common. I agree that it's functionally meaningless for street driving but it's cool to have people lay on the ground so you can point it out at a cars and coffee event. For circuit racing, it's VERY helpful because the majority of the time you're on corners and the poor diff is heating up whether or slowing or accelerating.

John

 

[Stevehose]

I agree that it's functionally meaningless for street driving but it's cool to have people lay on the ground so you can point it out at a cars and coffee event.

RIght, I want one even though not needed for a Starbucks run or anywhere else around here. But I'd have it "just in case"

 

[Krzysztof]

Correct me if I’m wrong. But are you saying that some side-loader differentials in the e9 cars have lsd but it’s not visible because there is no external reservoir and tube as you would see on cars like the m90 M 535i, and the early euro 635 csi? If so, it will be worth looking at my diffs for a hopeful lsd surprise. I. Reality, I don’t drive them hard enough to worry about it. It’s just cool to have

For me it is still "strange" that some E24 diffs with the external oil reservoir were not keeping lsd inside. Was it coming from BMW experience or was kind a gadget for some users?

 

[JFENG]

For me it is still "strange" that some E24 diffs with the external oil reservoir were not keeping lsd inside. Was it coming from BMW experience or was kind a gadget for some users?

In my limited experience, both an LSD and an open type diff will heat up at high speeds. With the much higher speeds in Europe (over 200kph), the not oil would both expand and foam more, and I guess BMW determined they needed a closed system to present oil loss over time. At the time, North American speed limits were 90kph. Just my best guess.

 

[Jon B]

For me it is still "strange" that some E24 diffs with the external oil reservoir were not keeping lsd inside.

In my limited experience, both an LSD and an open type diff will heat up at high speeds.

Heat and power loss from the rear axle occurs mainly through the pinion and crown wheel, and through the pinion and differential bearings.
This is especially true in high speed and competition driving. By comparison, the internals of an LSD operate at very low speeds.

 

[Krzysztof]

Thanks @JFENG & @Jon B for your opinion.

That makes sense of course to me.
Many E24 in EU were sold with "standard" differential (no oil cooler).
Taking into consideration Jon B opinion as the pinion and crown wheel are generating most of the heat, it could mean that the oil cooler would than be mounted on the higher ratio differentials as they have more teeth and thus in some specific situations can generate too much heat for the oil to keep the oil film stable, so they have been forces to use the cooler in such a specific differentials where low ration ones could still use standard system without any external cooler.
Of course later differentials used in E24 (and not only) were using different casing (inspection flap at the rear made out of aluminum alloy) which much better heat transfer due to different material and possible usage of the cooling fins, previous system was not able to use.

Differential I have is having such a ratio 3.25, so not so high.

 

[Dales]

One mechanic concluded that using the stamping on my housing, my VIN and production date, and his BMW shop manual I have a 25% 3.45:1 limited slip differential that is not functioning. Using that information and all of your responses, we decided to send the differential out for a rebuild. I will let you know how it turns out.

 

[Dales]

One mechanic concluded that using the stampings on my housing, my VIN and date of manufacture, the results of the spin test and his factory BMW shop manual I have a 25% 3.45:1 limited slip differential that does not function properly. Because of that information and all of your responses,we decided to send the differential out to be rebuilt. I will let you know how it turns out. Thanks again for your help. Dale