BMCGEE

We're back from Laguna, The ALMS and Yokohama finale. We were able to assist three more teams to championships in GT II, GT Challenge and Yokohama Gold Cup. Unfortunately we had one car out with a broken diff housing. It underlies the need to get all the cast iron housings out of the early cup cars, including 996 cups. I know it is hard to sell as a repair job when it is not broken but in the case of these diffs I think it is time. Ten to fifteen percent of these housings broke in '08. Expect that number to increase for '09.
Remember the importance of set-up for your particular application. That is something that we offer as the most qualified shop, having done more diff testing than anyone outside of Germany on Cup and RSR diffs. At Petite this year even Yoest had to come to BMC&G to solve a diff problem. That is because we have more diff data than almost anyone else. We have even done "back to back to back" testing with eight or more diffs using different configuration's, all set up with different ring gears fitted to the same car. Now we have a pretty cool computer program that can graph your diffs performance giving you a hard copy of your configuration in case you need to make an adjustment. To find out more about this just call Brian at 740-593-8936
BMC&G

Red9

What are the "cast iron housing" pieces referred to?

Mark Anderson

Having just broke my diff house a few months ago and it taking out my new r&p I completely agree.

Erik@GBox

Well as BMC&G has not yet registered as a sponsor here, I guess it is alright for me to post something here.

The pieces that he was talking about are the case itself that houses the internal workings of the differential. This is nothing new, however, and has long been an occasional issue with Porsche Differentials. They will usually show some cracking, if they do fail, from the windows on the side of the differential moving to the top or bottom. Sometimes they will actually fail by blowing the top completely off, or breaking the diff housing to the point of causing additional damage, usually to the ring and pinion.

Keep in mind the type of cars that Brian usually works on here though. These failures happen quite a bit more in the sequential gearbox, as the differential is taking quite a bit of shock as the gearbox moves from gear to gear. It is an issue, but I am not sure that it is quite as big of an issue as the general weakness of the differential in overall design.

The current Porsche Motorsport differential has only 8 plates in it. As a result a decent amount of preload is needed to keep the differential locked, and to keep it from getting smoked when you lift a wheel off the ground, or under high HP stress load. If you don't want to see this continue in your differential, or if you are simply tired of having to rebuild your differential a couple of times a season, GET the OS GIKEN!!!

I hope that this has answered your question.

Warmest Regards,


Erik Johnson
GBox Sales Manager
(303) 440-8899 work
(303) 895-4828 cell

Geoffrey

I gotta say that Rennlist sponsor or not, I really would only trust Brian's recommendations on gearboxes...Sorry Erik...also, OS GIKEN is not legal in PCA GTC classes.

PorscheII

Not only is Brian's opinion worth a lot more, but we heard the same excited sales pitch about Kaaz turds a year ago.

Glen

I would disagree.

While I respect Brian and Pam and their work greatly and have have obviously used them at times, and I am sure will again.

I also use Topp Racing for gearbox stuff currently and am pleased with that solution also.

I also respect and appreciate the options and information that Erik is putting together as alternatives for all of Us.

I would think he would/should receive a warmer reception as he has abided by all the rules of Our forum...

Erik@GBox

Geofrey - After careful reading of the rules it seems that you correct that NO differential other then the provided factory differential is allowed, so it makes the original post here with regard to changing out the differential a moot point, as well, at least for GTC. I have not seen any other class where using the OS Giken differential would be an issue, so perhaps with the associated issues with the current cast iron stock differential, they will make a modification to the rules. That is not for me to say though.

As I understand the rules of PCA, which perhaps I have mistaken, if it does not say you can do it, then you can not period, correct? So that being understood, it does not say that in GTC you can change anything in the transmission. It has to remain exactly as it came from the factory.

Super Class - GTC
All non-street legal factory Cup Cars as delivered from the Porsche factory to meet Supercup or Carrera Cup specifications without modification except as provided below.

There are no additional modifications listed related to the transaxle, so I understand that to mean that you can only use what came with the car. This would make the modification that BMC&G has posted here illegal as well.

Can someone confirm this for me though, please? I would really like to know for sure exactly how this works so that I do not mistakenly recommend something to someone who is not supposed to use it. I would hate to contribute to a rules violation, as there is supposed to be a degree of honor in PCA Racing right?

Thanks for the post, and please do not misunderstand my words here. I have the utmost respect for Brian and BMC&G. They have all been doing this for some time and have a long time reputation for working with several different racing groups. However, I have been warned time and again in the past that posts such as the one here, were absolutely not allowed unless I became a supporting sponsor of this site, which by the way is not cheap. In that agreement it clearly states that as a sponsor I can not make comments on other sponsors threads, as BMC&G has not made this move to sponsorship as of yet, I felt that the question posed by RED 9 as well as the original post by BMC&G deserved a bit more information. I did not post my opinion to counter the original post, only to give it a bit more detail.

Please allow me to apologize if I somehow offended your sense of right and wrong, with regard to this issue, that certainly was not my intention.

PorscheII - I agree with you that my enthusiasm for the Kaaz differential a year or so ago may have been a bit overstated, however that being said, it should be noted that the OS Giken is not a Kaaz. Please also allow that with time comes wisdom, and I have been fortunate enough to have been granted a bit of both. If you don't like the OS Giken, that is fine, but I really do not think it appropriate to disregard it due to the past sales efforts of a dedicated individual, such as I am, to make a living, and give people here a choice, especially when the choice offers as much as this new differential does.

Thank you all for your comments, I truly do appreciate them.

Warmest Regards,


Erik Johnson
GBox Sales Manager
(303) 440-8899 work
(303) 895-4828 cell

Erik@GBox

Geofrey - After careful reading of the rules it seems that you correct that NO differential other then the provided factory differential is allowed, so it makes the original post here with regard to changing out the differential a moot point, as well, at least for GTC. I have not seen any other class where using the OS Giken differential would be an issue, so perhaps with the associated issues with the current cast iron stock differential, they will make a modification to the rules. That is not for me to say though.

As I understand the rules of PCA, which perhaps I have mistaken, if it does not say you can do it, then you can not period, correct? So that being understood, it does not say that in GTC you can change anything in the transmission. It has to remain exactly as it came from the factory.

Super Class - GTC
All non-street legal factory Cup Cars as delivered from the Porsche factory to meet Supercup or Carrera Cup specifications without modification except as provided below.

There are no additional modifications listed related to the transaxle, so I understand that to mean that you can only use what came with the car. This would make the modification that BMC&G has posted here illegal as well.

Can someone confirm this for me though, please? I would really like to know for sure exactly how this works so that I do not mistakenly recommend something to someone who is not supposed to use it. I would hate to contribute to a rules violation, as there is supposed to be a degree of honor in PCA Racing right?

Thanks for the post, and please do not misunderstand my words here. I have the utmost respect for Brian and BMC&G. They have all been doing this for some time and have a long time reputation for working with several different racing groups. However, I have been warned time and again in the past that posts such as the one here, were absolutely not allowed unless I became a supporting sponsor of this site, which by the way is not cheap. In that agreement it clearly states that as a sponsor I can not make comments on other sponsors threads, as BMC&G has not made this move to sponsorship as of yet, I felt that the question posed by RED 9 as well as the original post by BMC&G deserved a bit more information. I did not post my opinion to counter the original post, only to give it a bit more detail.

Please allow me to apologize if I somehow offended your sense of right and wrong, with regard to this issue, that certainly was not my intention.

PorscheII - I agree with you that my enthusiasm for the Kaaz differential a year or so ago may have been a bit overstated, however that being said, it should be noted that the OS Giken is not a Kaaz. Please also allow that with time comes wisdom, and I have been fortunate enough to have been granted a bit of both. If you don't like the OS Giken, that is fine, but I really do not think it appropriate to disregard it due to the past sales efforts of a dedicated individual, such as I am, to make a living, and give people here a choice, especially when the choice offers as much as this new differential does.

Thank you all for your comments, I truly do appreciate them.

Warmest Regards,


Erik Johnson
GBox Sales Manager
(303) 440-8899 work
(303) 895-4828 cell

Erik@GBox

Not sure why this posted twice, sorry about that.

PorscheII

Has he ? Not only have his numerous ads contained "facts" that sound more like opinions, but he has dissed both Porsche and Guard/GT LSDs ... or does "vendors" only mean "sponsored vendors" ? I ask because I don't know for sure.

In general a maximum of two ads per month may be posted.

Vendors are cautioned not to disparage other vendors, or the products/services they may offer.

Erik@GBox

PorscheII - I realize that I can not please everyone here, but I will try again here. "Vendors" does in fact mean "sponsored vendors" and with regard to dissing, I guess I fail to see your point, a superior product is simply superior, which this one certainly is when comparing it to either the Porsche Motorsport differential, or even the Guard Differential. You may call it opinion if you wish, but that simply tells me that you may not have enough facts to make a educated decision either way, this would be my fault probably. That being said allow me to repost a direct comparison between the three as you may not have seen this in a different room.

Believe me I understand where everyone is coming from here, but take a look at the OS Giken here, and I am sure that you are going understand where I am coming from with regard to saying that even the GT differential, which has always been a very good option in the past does not hold a candle to this differential.

A very bold statement I understand. But since it has been now brought up- here are some things to consider when comparing these three.

The GT Differential has always had a similar design the Porsche Motorsport differential, that being a plate type ramping differential. It made it's mark here with the ability to custom choose between two different ramp angles within the same differential. Usually 40/60 and 80/80 but certainly a couple of other options as well. It also features 4, 6 or 8 plates internally, that is 2, 3, or 4 plates per side. It also features a more aggressive friction composition to that of the Porsche Motorsport diff.

Here is the rub. The GT differential has on average a 65 to 85 lbs. breakaway preload. This has shown to cause a couple of issues. The first being that as you enter into a tight turn your car has to overcome this preload in the process of turning in. So what right? That should not make much of a difference. Well actually it does. The more preload there is the harder it will be to get the car to turn, but this is not usually much of a problem as you get used to the differential, and modify your driving to compensate. What is a problem is the material that is removed from the plates inside the differential ever time this happens.

The Porsche Motorsport differential utilizes carbon as the primary friction material in their differentials, the GT diff does not. They use a moly blend, which is then plasma sprayed onto the plates to cause a friction material. This material is highly coarse and reacts in a way to not only lock the differential, which is good, but also remove metal from the opposing plates, which is bad. This combination of friction material and removed metal goes where?? Through out the gearbox, very bad. It especially goes directly into the input and pinion bearings, where it begins to cause problems inside of them as well. VERY VERY Bad.

So how is the OS Giken different? If you review the pic here, you will see that on the ramps themselves are counter springs that help you pull the ramps back to neutral when there is no force applied to them. It essentially reduces the breakaway to a very minimal amount, it basically opens the differential up, releasing the plates, so that you do not get unneeded lockup, and as a result unneeded wear. The friction material is again carbon, but due to the amount of plates which is more then double the GT or the PMS, as well as the way the differential works, they do not suffer from premature wear. Nor do they require the rear of the car to overcome excessive lockup in order to turn the rear end. (the difference in speed between the left and right tire.)

I understand that in the past we have all, including me always gone to GT for the strongest best differential made. I have for years recommended only them for racing applications. However with this new offering, as well as the difference in cost between the three differentials, I can not see how anyone could still do this.

GT Differential, $2,400 to $2,800 give or take.
OS Giken Differential $1,790.00

In the nine year that OS Giken has been making differentials, they have exactly ZERO failures. Now to make this completely understood, that is not just in their Porsche diffs, that is for ALL of their differentials across the board. That to me is pretty impressive.

Check out this pic, I think that if you have ever been inside of a Porsche LSD, no matter who built it, you will see, there is no comparison, and for the moment, no competition to this differential.

Okay so I think you can get a better idea now why I say that this is far superior differential. As to facts, well these are facts, and not opinions, should you disagree I would recommend that you call Guard and ask Matt yourself, I know I did, just to make sure that I did in fact, have the correct facts with regard to the preload settings, and plate composition.

I am sure that you will still want to discuss this in detail, and so long as this does not result in a pissing contest, which no one ever really wins, I am happy to continue our conversation.

If for some reason you have something against me, by all means I would love to know what that might be, but I would recommend that you PM those comments, as I doubt that anyone here really wants to read it.

One last thing, just for your information. Here are the rules as they were recently emailed to me here when I registered to be a supporting vendor:

DO:

Begin a sales thread
Respond to a user's query for a product or service
Respond with a group buy, if needed
Display sales and links in your signature

DO NOT:

Post anything on another vendor's sales thread

I do not see where your previous comments are listed here, as such I hope that you will forgive me for not paying them due attention, perhaps the rules have since changed when Internet Brands took over the forum. To that I am not sure.

Warmest Regards,

Erik Johnson
GBox Sales Manager
(303) 440-8899 work
(303) 895-4828 cell

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

Geoffrey

Good post Paul, thanks.

wickerbill

sorry, my inglish isnt so good but Paul Guard is xacttly correct abot the tests on LSD with Motorsport. Also, I have used a GT LSD in Germany unt found it to be very very excellent unt very predicable. Paul Guard has experince.

Thank you