Hello,
We just recently got a Cayman S LSD into the shop and took it apart for the first time. Since this is the first one of these we've seen, I figured I would take some pictures and do a little show and tell with this thing.
Here's the LSD from the outside:

Looks pretty normal for a factory LSD. Cast body, but nothing out of the ordinary. Then we take the cover off:

Here's where it gets a little interesting. Notice that it is in fact a 4 plate LSD, just like a GT3 or any of the other modern Porsche 6MT gearboxes. But, look closely. The friction discs are stacked one on top of the other. Here's the stack as it comes apart:

It goes plain plate, plain plate, friction disc, friction disc, plain plate. So, even though it's got 4 friction discs it's only using 2 of them. Reminds me of another Porsche LSD:

That's a picture of a 1970 911 LSD!!! There's also another similarity between the old LSD and the new one; no belleville washers.
This new Cayman S LSD is a zero preload LSD. In fact there's absolutely no gap inside of this thing. The stack height is pretty much exactly the same dimensions as the body and cap of the LSD. I know there's been much discussion recently about low or no preload LSDs. I'll let you guys debate the merits of those designs, but will ask one question on the subject. If a no/low preload LSD is the way to go, why did Porsche stop using it? And as a follow up to that thought, why now, roughly 25 years later have they gone back to it?
I've got more thoughts and pictures, and will follow up with another post in just a second here...

 

So, the next thing I did was start to look at the internals themselves. They've gone to a new type of friction disc material. I'm not quite sure what it's made out of, but it's a new approach for sure. Maybe they are getting their friction materials from brake technologies. I don't know. If you look at the picture, not only is it some sort of fiber material (reminiscent of the 933 carbon friction discs) but it's "pucked" with the friction material attached with some sort of adhesive:

If you look closely you can see that there's wear on the plates, so it appears that it does bite marginally better than the brass being used in the GT3 LSD:

But what really stood out to me was the size of these parts. They are teeny. Like 904 LSD teeny!


Versus the old 1970 911 LSD (from a car with roughly half the horsepower of a modern Cayman S):


Versus a modern day GT3:


It just doesn't strike me as very much friction surface for locking this thing. But if you look at the ramp angles, they don't really intend this to have all that much lock:

versus the old 40/40 angles of the 911 LSD:

So what's the plan from here? Redesign it so that it works. This came out of an Interseries car that had one season of racing on it. The car owner reported that he was spinning his inside tire for pretty much the second half of the season last year and was effectively running with no LSD. Guys tracking these cars seem to be burning them up really quickly. Our attitude is that there's really no reason anyone who's got one of these units should have to throw it away, so we're going to make parts for it. And having recently gotten our hands on a PDK LSD, it's effectively the same design and same parts, so it will take care of those owners as well.
Please feel free to add your own analysis to what you are seeing and ask any questions that might come up.
Kind Regards,
Matt Monson
Guard Transmission LLC

 

Nice write up!

 

How do you think this unit compares to the quaife LSD and other aftermarket offerings in terms of perfoprmance and longevity ? Are there only issues when using these units on race series cars or would you expect road cars to also experience them wearing out ?

 

Hello Berty,

Based on the feedback that I am getting from car owners, I would say that if you drive your car aggressively on the street you'll have the same issues that the track guys do. Last month I had a new Cayman owner call me from California telling me that he had less than 500 miles on his car and decided to go for a spirited drive up towards Big Bear in CA. He complained that he was spinning the inside wheel on pretty much every tight corner he got into and tried to leave at full throttle. If you don't drive your car that hard, then you probably have nothing to worry about. Though if you don't drive your car that hard, you can also probably save yourself the $800 and order it without the LSD if you haven't already made the purchase.

So, in that respect any aftermarket differential will be more durable. That's because they will actually work the way they are supposed to. However, I do want to clarify one point. Quaife differentials are not limited slip differentials (LSDs). They are what are known as a torque sensing or torque biasing differential and have significant performance differences from a true LSD. Here's some good reading of a discussion on the topic:
http://www.planet-9.com/cayman-boxst...sd-vs-tbd.html
If you're left with any questions about their function or anything else, please don't hesitate to come back and ask them here.

Here at Guard Transmission, we do make both a LSD and a TBD for the Caymans. Depending on particular application and usage one versus the other may be most appropriate for you. Let me know if I can offer any input on what might work for you personally and your needs.

Kind Regards,

Matt

 

Thanks for the initial thread and link to the caymanclub article. Though I don't track my car, I've owned cars in the past with LSD / TBD such as an RX7 13B (the 944 lookalike). I'm not sure what the technology was on that particular car, but it made for some enjoyable experiences and no doubt saved my bacon on more than one occasion.
For my boxster I'm considering keeping it long term and as a result would consider an LSD/ TBD as an enhancement. The main reason to prevent those embarassing inside wheel spin moments when turning out of a junction with some enthusiasm.
Obviously I need to read up a little more on the technology before making a decision based on price and availability of which hardware suits my needs best.

Thanks again .

 

Do you have solutions for PDK equipped Caymans?

 

Hello rubber_ducky,

It does appear that the factory PDK LSD uses the same internal parts as the 6MT LSD, so when we make internals for that LSD it will cross over.

However, at this point we have no plans to produce an actual differential for the PDK. There's just been next to no demand and we don't consider it a motorsports component. If people were to start racing them, we would look into it, but that hasn't happened yet. Right now the people racing in Grand Am, Interseries, and PCA are all running 6MTs and most of the are using our LSD over the factory unit. We'll support what's being used, but people have to start using the PDK at a Pro or Semi-Pro level to get our interest. Either that, or there has to be a huge groundswell of street rodders who want the parts who are willing to make a commitment to buy and then be willing to wait the 4-6 months it takes to develop a new product.

 

Thanks for the informative writeup! I just pulled the trigger on on '08 Cayman S and one of my big hangups was whether to look for an '09+ with the factory LSD or just go aftermarket when the time came. After reading this, I'm glad I went with the '08 that I liked and have choices for the diff.