Originally Posted by SamboTT@ByDesign

You are having fun with it. That's what really matters. As long as you don't start going into uncontrolled maniacal laughter on an hourly basis and calling everyone "Pilgrim" with one eye almost shut.

Fun share...Good luck Dude

Originally Posted by joe731

Has anyone sorted the differences between the 997 Cup LSD and the Guards LSD?

Any clear benefits in one versus the other? Cost difference?

Originally Posted by Paul Guard

Although I am retired from Guard Transmission, I don’t like hearing that the products I helped develop are being held up in a negative light. Let me correct the inaccuracies that have been excitedly presented as facts.

First of all, only Porsche street cars (intended for street use) come equipped with carbon friction discs. Track use will fry carbon friction discs pretty quickly, which is why all Porsche track cars utilize a far more aggressive friction disc (far more durable and functional than a carbon disc). When I was with Guard Transmission, I would rebuild perhaps 3 or 4 Porsche street LSDs each week, replacing the carbon discs with our own Motorsports style discs (which also require using our harder REM plain plates). This makes a street LSD far more trackable, although certainly not on par with a complete Motorsports LSD (whether that be a Porsche Motorsports or Guard/GT unit).

Given the fact that a good used Porsche street LSD upgraded with Motorsports style friction discs will perform properly for many times longer than any LSD equipped with carbon friction discs (30,000+ miles for street use), no shop should ever talk their customer into replacing an OE street LSD with a less versatile product. And, if they should sell that customer any aftermarket differential without offering him something for his removed OE LSD core (or returning it to him to sell on e-bay), well … that just isn’t right.

Regarding the number of plates in an LSD: In my experience, the number of plates makes little difference in the service interval of any LSD. Service intervals are far more affected by the type of friction material in the unit. (In every street LSD with carbon discs that I’ve rebuilt, the service interval was at least quadrupled by replacing the carbon street discs with Motorsports style friction discs … and as I‘ve already said, performance was greatly enhanced at the same time.) Although my company used to offer an LSD that would accept 24 plates (12 friction + 12 plain), we never had a shop ask even once for this many active discs to be installed. The Porsche engineers (who are pretty smart guys), have never seen a need for more than 8 friction discs (+8 plain plates) in their Cup or GT3RSR race cars.

It’s worth stressing again that a conventional LSD can be set up in any number of ways by varying plate, disc, and belleville washer thickness, number of active friction discs, ramp angles, etc. There is no single set-up that is perfect for every user, so the ability to adjust an LSD to different settings (and the ability to later change those settings) is important to most shops, and certainly to any race team. Set-up versatility in any track LSD is essential. Any Porsche owner who has only an open diff will of course see some level of improvement with almost any LSD or TBD that they choose … but the smart owner who’s interested in aftermarket differentials, will only deal with a mechanic who can intelligently discuss the pros & cons (quality, price, intended usage) of each choice with him.

When it comes to LSD and suspension set-up, BMC&G is by far the most experienced of any shop in the U.S. Since Brian has taken LSD tuning to a new level through his interaction with every U.S. Pro race team as well as Porsche engineers in Weissach, I naturally value his opinion on various LSD types more than any other shop. According to Brian, extensive testing was performed by Porsche Motorsports in which he was the service technician … once in early 2008 with an ’07 GT3RSR, and again in late 2008 with an ’08 GT3RSR. Porsche gathered every different LSD type that they could find … factory LSDs, aftermarket LSDs, high priced LSDs, moderately priced LSDs, and even one low priced LSD. Onto each of these LSDs was installed a ring gear*, bearings, and the required shims. Each LSD was pre-measured and set up to quickly fit into the same transmission. (*Eight R&P sets were selected with identical R factors, because comparative testing had to be performed in a single day.) Different pre-measured internal disc and plate stacks were assembled for each tunable LSD, which would allow for quick changes in stack preload (breakaway torque) during the test period. The drivers were shielded from knowing which unit they were testing or not testing. Each mini test session was comprised of a 5-lap run, with all results being data logged. There was about 20 minutes spent between each test session installing a different LSD.

1) The lowest lap times and highest driver satisfaction were obtained with Ricardo's new viscous type LSD. This is a near perfect LSD for a number of reasons that don’t need to be fully explained here. Suffice it to say that the ultimate in performance does not come cheap. The cost of this LSD is well over $20,000.

2) A group of LSDs virtually tied for a very close 2nd place behind the viscous unit. These LSDs all had high breakaway torque settings, with the only exception being a very high quality German made LSD with zero preload. All of these LSDs had Motorsports type friction discs. While the handling characteristics of the car varied slightly between LSDs, the lap times were virtually identical.

3) Further testing was performed using lower breakaway torque values with any of the above LSDs that would allow such adjustments. In each case, lap times were significantly slower at these reduced pre-load settings.

4) Singled out by its slow lap times and worst exit understeer characteristics was the lowest priced LSD. Porsche actually spent a little more time testing this unit than some of the others, because they were intrigued by the low cost … not because they were impressed with its “counter springs” or the 20+ plates in it. However, each time the driver was sent out with this unit, he returned to the pits with a “thumbs down” in regards to its track performance. Obviously, no Professional Porsche road racing team would ever run one of these LSDs, despite its low cost.

When the day comes that a vendor can truthfully claim that the LSD they retail has replaced Guard’s as standard equipment in every RUF Rt12 Turbo, I will concede that this product is probably as strong as a GT LSD. When that vendor can further claim that their LSD has replaced Porsche’s LSDs in Professional road racing cars, I will also concede that this is the new standard by which LSD comparisons should be made. In the meantime, I feel that I am certainly within my rights to defend any product (that I helped develop) from being unjustly slammed on Rennlist by one of its sponsors.

Paul Guard


______________

“Remember Jerry … it isn’t a lie, if you believe it.” George Castanza, Seinfeld

Originally Posted by joe731

Wow. Great info.

You are the dude!