Anyone know an estimate on price for this conversion parts wise? Thanks.

 

That is a varible that largely depends on which diff you go with. The crbonetics are supposed to be pretty good and go for ~$1200. The rest range from $1600->$3000. The guard diff go for just under $3000 and is uses by many porsche race teams. Most shops charge 8 hours to do it. You will want to replace the stub shaft seals, diff cover seal and both bearings. You will need to have spare assortment of shims for setting the correct bearing preload And backlash.

 

Definitely following this as it's been on my to-do list for awhile. Great info so far!

 

Okay, so I picked up a used factory porsche GKN LSD w/ stock GT3 plates for $500. What a remarkable piece. I am debating whether to keep the stock gt3 vanes which are in good condition, change to the Cup car vanes which are supposed to be a more aggressive setup or the Guard vanes. I have yet to measure the preload on this diff yet to guage it's condition.



So, I would like to brainstorm a little on the Factory LSDs and their inherent issues. It is commonly know that they have been known to "fail" with next to zero preload after a single track season. The preload in itself is not a single indication of the effectiveness of the LSD. In fact older porsche diffs ran zero preload without a belleville washer, which was later changed back to a preloaded setup. A differential with no preload will still lock. It will however require more ramp plate outwards movement to accomplish the required lock. The preload check does serve as an indicator of the wear of the diff though. One thing that I have found in my research is that many of the LSDs that have been rebuilt have shown the vanes to be in good condition. And the plain vanes have been measured to be lightly worn with no detrimental wear. So my question is, if the vanes are not toast in all instances and the preload is the varying factor is the belleville washer the weak link and the solution for mostly street driven cars? I am not a differential expert, and I am hoping to understand the wear patterns and weak links of these diffs. And hopefully help others. For those needing a little info into the stock GT LSD setup, read this: https://www.6speedonline.com/forums/...sd-buster.html

 

From what a lot of guys are saying at the track is that the stock GT3 LSD is a joke and pretty much useless after a few track sessions. The problem is that many people don't realize they have a weak LSD until they get it rebuilt and can experience the difference. The stock LSD I believe has a pretty mild locking factor from the factory. I'm going with a guard 40/60 diff and my shop is currently putting together a cooling system for the gearbox. I'm looking forward to getting this installed as I get a lot of wheel spin on my inside rear tire in the tight corners at the track. I would talk to Matt at Guard with any questions, he is a wealth of information.

 

Yeah, the lock up is mild due to the friction plates. However, for my driving I believe mild is what I need because I drive my car daily. I do not need the most competitive setup. I need something better than an open diff. Obviously cost is a factor as well. The best is not an option I want to pay for.

That aside, I do believe that their are improvements that can be made without going with all new internals. One being the Belleville washer being upgraded to one that does not compress and flatten over a short period of time. Possibly a higher preload as well. But, the higher the preload, the more wear. So essentially I would like to find a happy medium between stock gt3 and a guard rebuild. And hopefully discussing this will also educate the curious minds here on the forum.

 

Hey VAG, are you converted RWD with an open diff right now? The reason I ask is that I'm AWD and do not have any traction issues on the street with an open diff but on the track I do. I just can't imagine being able to safely push the car hard enough on the street for an LSD to be needed. On the track absolutely. If you're RWD with an open diff than absolutely it would help.. Just curious. For a street only driven car I would consider a TBD over an LSD since a TBD will not create as much added heat to the gearbox as an LSD especially if you're not planning of some kind of a cooler. It's also much cheaper.

 

I am RWD with open diff. The traction issues are only on hard cornering since I went with a more aggressive tire. The Pirellis just were not cutting it.

Edit: Also, I do intend on a few track events. But not regular. Just educational.

One other thing I was just now read was you comment on not knowing the diffs were done until they drove a properly setup one. The Guard setup is an improvement over even a brand new stock healthy Porsche LSD. I had an interesting conversation with someone at California Motorsports on the stock LSDs and he mentioned that the diffs were not failing early. They were either not aggressive enough or the plates were worn as normal for the mileage and use. All diffs will need an overhaul at some point and the interval is a variable based on the type or use.

 

I suggest you take a good look at the pictures and explanations I have posted in the LSD buster thread. The ones with blue burned up plates are 997 GT3s. The ones with catastrophic failures of the gears are GT2s. With RWD and your power levels if you don't rebuild that LSD you acquired you will either blow it up or significantly decrease the service life of your whole gearbox. The blue is from the heat generated when the anemic friction discs in the factory LSD just slide and slide and slide against each other. the ones that blew up are ones that were allowed to run hot like that long enough that the internal gears were compromised from the heat and self destructed.

I know that some people are proposing that new bell. washers can fix the problem. I do not agree with this line of thought. The thinnest high performance bell. washers you can get to upgrade with are 1.8mm thick. The stock ones are 1.15mm thick. The average internal gap of a factory street LSD is around 2.0mm. The internal gap of a Cup Car LSD is .7-.8mm. Do the math. If you "upgrade" the bell. washers what you've done is tightened your street diff down to Cup Car spec. Does it produce an LSD that "works"? Yes, but it's going to have more static lock and worse street manners than if I rebuilt it.

I don't know where people got the idea that when I rebuild an LSD that it's not streetable. That's total rubbish. When these units come to me I know exactly how the car is going to be used and what its percentage of street versus track usage will be. I encourage you to post a question directly to the LSD Buster thread asking how many people drive the car on the street and what their experience has been. I suspect that you will be told that for the people who street drive their car pretty much don't even notice the LSD has changed. I only build a racing configuration into a racing differential. If the car is a trailer queen that's part of what we call the DE Cup, that guy gets a different build than the guy who tracks the car 4-5 days a year and otherwise drives it 5 days a week. It's part of what makes us different. If you call your Porsche dealer, he will sell you a "vane kit". It's always the same thickness. When you call me, you get a custom stack that is more agressive than stock but not built like a Cup Car. And I microtune it from there. When I change the stack height by as little as .2mm or the bell washer thickness by as little as .1mm, it changes the differential significantly.

 

I never heard anybody say your diffs are not streetable. The vanes in my diff are in great shape and are not burnt. The friction plates and steel plates look almost new. If the vanes were done the decision would be pretty cut and dry.

I am curious of one thing that maybe you can answer. It is well know that Porsche does not tune these differentials. If the vanes are in good condition, is it still impossible to improve upon the differential without replacing the internals with your vanes? It won't be as good as your setup, but will a properly tuned diff with stock friction disks really expload on a mostly street driven car? If so, why are the forums not plagued with these posts like they are with RMS leaks, 2nd gear popout, coolant hose failures and intermediate shaft noises? I think your product is top notch, but I cannot justify spending that on a stock diff when I can just buy an aftermarket unit.

 

I think in the end, as the old saying goes, you end up getting what you pay for. I've learned one thing and that is the simple fact that if you are going to do something to improve the performance of these cars you either do it right or don't do it at all. I've been down that road before.... In any case, hope it all works out and let us know how it turns out in the end.

 

When you put a lsd in a non gt car you have the psm to think about.. It will stab the brakes and tax your lsd.. PS that how most of the "high hp" turbo cars break the lsd.

 

Matt,

I have a gt3 lsd and while the motor/trans is out I would like to upgrade. I am mostly straight line but am thinking about time attacks. What do you suggest. you can pm if you like. Thank you in advance.

Tim

 

Who is talking about buying an aftermarket unit? The whole LSD buster thread is about rebuilding the factory LSD so that it functions properly. So you spend $300 on bell washers and steel plates to make it work moderately well with the stock friction discs. Or you spend another $500 beyond that to put our clutches in there while you are in there. Seems like splitting hairs to me.

I maintain that the brass clutches in the stock factory LSD are pretty much junk. Even the cars that I've seen that do the "Cup Car" stack I described in my post above generally come to us a year or so later asking us to fix their annoying loud and poorly functioning LSD. You ask why the forum isn't "plagued" with posts about the problem? I've rebuilt more than 500 of these units and the LSD Buster thread on this site has over 35,000 discreet veiws. The one on Rennlist is just as popular.

Maybe you think I'm just trying to sell you something. So be it. The reality is that I am like the guy in the old Norelco commercial. I believed in the product so much that I bought the company. You know from first hand experience that I gave you more than 20 minutes of my time on the phone with no pressure to buy something. I gave you free advice. If you spend $800-900 with my company has very little effect on my bottomline. Unlike many vendors who post here with the exclusive agenda of selling you their product, I try to keep my posts more informative than commercial. I am telling you that if you keep the stock brass discs, regardless of how perfectly new they appear, you will regret it later. And the beauty of free advice is you are free to accept it or you are free to ignore it. Either choice is free.

 

I did not mean to start a **** storm about this. I really don't think it is fair to assume that i am questioning your intentions. I just want feedback from other people who has been down this road that can share their experiences. My question is can a properly tuned differential with stock friction vanes be an improvement over the factory stack up? You mentioned that the stock setup will fail or blowup and damage the transmission. All I wanted is clarification. I know that if you rebuild my diff it will be top notch. All I am seeking is knowledge, understanding while hoping that others here can benefit from it. This isn't a "guard wants to take your money, run away!!!" thread. Don't take it personal. I think everyone here will attest to your excellent knowledge, product and prominence in the racing scene. But, to simply say that a stock diff will blow up don't use it with the stock internals is cryptic and does not help others fully understand all of the issues of the diff. Their have been people who have tuned and improved upon these with the stock friction discs. Those were the guys I was hoping to here from. If those people pipe in and say " yeah, it was a complete failure and it came out a year later for a rebuild", then that is it.