LSD buster
04-16-2010, 05:49 PM
#61
Nordschleife Master
Given that I have never heard of this problem on a 996 LSD I don't think I'm going to change my recommendation. I think there's a lot to be gained on the 997 by changing the ramps because of the increased locking rate. The 996 is 40/60 already and I haven't seen them chip so I'm not going to just sound the alarm and tell everyone they need new parts. I'm not the kind of guy who will sell you something just because it makes me some money. That's not how I work.
As I've thought about this more, something to consider is whether or not there's a correlation between the amount of wear on this particular LSD (that huge gap I was talking about) and the posts being able to get into a position to chip the ramps. It may be why I've never seen if before. I reviewed my build sheets ( I keep an index card on every LSD I build, customer rebuild, or GT new product) and I've never had a 997 LSD with more than 1.8mm gap before. That extra mm of wear may be what allowed the post to push the ramps far enough apart to cause that chipping.
For customers who mostly street drive their 997 GT2 and GT3 cars I'll probably continue to give the same advice I've always given. For those people replacing the ramps is really an optional thing that they don't really need to do. It's the track day junkies and racers who need to give serious consideration to changing the ramps, which is still advice I would give more from a performance perspective than from a concern that their ramps are going to chip.
As I've thought about this more, something to consider is whether or not there's a correlation between the amount of wear on this particular LSD (that huge gap I was talking about) and the posts being able to get into a position to chip the ramps. It may be why I've never seen if before. I reviewed my build sheets ( I keep an index card on every LSD I build, customer rebuild, or GT new product) and I've never had a 997 LSD with more than 1.8mm gap before. That extra mm of wear may be what allowed the post to push the ramps far enough apart to cause that chipping.
For customers who mostly street drive their 997 GT2 and GT3 cars I'll probably continue to give the same advice I've always given. For those people replacing the ramps is really an optional thing that they don't really need to do. It's the track day junkies and racers who need to give serious consideration to changing the ramps, which is still advice I would give more from a performance perspective than from a concern that their ramps are going to chip.
04-17-2010, 01:01 AM
#62
Rennlist Member
Appreciate the information and hope Porsche AG sorts this out quickly. Maybe their vendor made this component improperly or at least one bad batch. The racing teams will sound off for sure.
04-17-2010, 12:24 PM
#63
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So here's a few photos for your review:
See the chip? See the hairline crack on the upper side that suggests that one is about to break off as well? At first I thought it was some weird fluke. But it's on 3 of the 4 posts!!!
Also, here's what the gears look like. See the pitting? The crazy thing is that I have brand few OEM LSDs showing the same inconsistencies in the gears. The spider gears are going to be the next thing to go on these LSDs. And this is one thing that's no different on a motorsports LSD. The same gears are used.
Lastly, I want to show you what happens when these get driven hard and are really done. While the mileage on this car is very low, this owner pretty much tracks the car and not a lot else. For reference, Mikymu's LSD had an internal gap of less than 1.6mm. That's pretty typical. I see them from a low of 1.3 or 1.4mm when brand new to around 2.0mm when worn out. This particular LSD had a 2.8mm gap!!!
And this is what happens with that gap. It gets hot. It gets really hot because the plates are just spinning in there and not biting on each other. This is what happens if you keep driving on it once it's worn out.
See the chip? See the hairline crack on the upper side that suggests that one is about to break off as well? At first I thought it was some weird fluke. But it's on 3 of the 4 posts!!!
Also, here's what the gears look like. See the pitting? The crazy thing is that I have brand few OEM LSDs showing the same inconsistencies in the gears. The spider gears are going to be the next thing to go on these LSDs. And this is one thing that's no different on a motorsports LSD. The same gears are used.
Lastly, I want to show you what happens when these get driven hard and are really done. While the mileage on this car is very low, this owner pretty much tracks the car and not a lot else. For reference, Mikymu's LSD had an internal gap of less than 1.6mm. That's pretty typical. I see them from a low of 1.3 or 1.4mm when brand new to around 2.0mm when worn out. This particular LSD had a 2.8mm gap!!!
And this is what happens with that gap. It gets hot. It gets really hot because the plates are just spinning in there and not biting on each other. This is what happens if you keep driving on it once it's worn out.
Matt , these look awfull!! i cant beleive i was driving it!! If it was not for this thread i would still be driving the cars hard... until the chipped parts find there way in the gearbox ...... are these the GT3 or GT2s LSD?
If its the GT3s , it only saw 2 track days!! , While the GT2 had 3 track days only... all of them hav about 6000 miles on them!!
Where the damage similar on both? i guess the GT2s lsd would be the one with most damage since it had higher hp and tourqe than the GT3 ?
If its the GT3s , it only saw 2 track days!! , While the GT2 had 3 track days only... all of them hav about 6000 miles on them!!
Where the damage similar on both? i guess the GT2s lsd would be the one with most damage since it had higher hp and tourqe than the GT3 ?
04-17-2010, 02:19 PM
#64
Rennlist Member
Wow--these pics are very helpful (if not shocking).
Anecdotally, my failed diff (which is now with Matt for a rebuild) appears to have caused quite a bit of overheating in my tranny as well. Despite my frequent tranny oil flushes, the fluids all come out like murky black coffee, with fine metallic dust in the "brew". And this last fill only saw 800 street miles! FWIW I use mainly Redline 75W90 since Mobil Delvac / PTX isn't quite available in my neck of woods...
Matt when you get around to it, I wouldn't mind if you post the pics from my rebuild so we can all get a sense of how the OEM parts fare...
Anecdotally, my failed diff (which is now with Matt for a rebuild) appears to have caused quite a bit of overheating in my tranny as well. Despite my frequent tranny oil flushes, the fluids all come out like murky black coffee, with fine metallic dust in the "brew". And this last fill only saw 800 street miles! FWIW I use mainly Redline 75W90 since Mobil Delvac / PTX isn't quite available in my neck of woods...
Matt when you get around to it, I wouldn't mind if you post the pics from my rebuild so we can all get a sense of how the OEM parts fare...
04-20-2010, 01:20 PM
#65
Nordschleife Master
Hello,
I had a 996 GT3 LSD through the shop yesterday and figured I would use that to show you the differences I am talking about with respect to the inner gears that are going in these LSDs. I've already posted a 997 GT3 spide gear above. Below is the 996 gear. You can see that they used to be billet and properly ground, like a gear should be.
And here's the side gears, side by side. One is a used 996 gear and the other is a brand new 997 Cup side gear. In case it's not obvious, the lower gear is the 997.
The old style gears are definitely wearing better than the new cast gears they are using. I just put it out there because it's something you should consider for the future that you are going to need to service on these differentials. And it's not something that is resolved by upgrading to a Cup Car LSD. I've been getting asked a lot why someone should buy our $2700 LSD when they can get an 8 plate Cup Car LSD from Porsche for the same price. Well, this is the answer in pictures.
Something that would be worth exploring would be what exactly one gets if they order the side gear and spider gear service packs for a 996 LSD. If the old gears are what fall under that part number, it may be a cost effective way for people get the better gears in their LSD. But my gutt feeling on it is that like purchasing our gears separately, it's likely not cost effective and probably going to point people towards the direction of buying an all new LSD at the point that their spiders wear out.
Regards,
Matt
I had a 996 GT3 LSD through the shop yesterday and figured I would use that to show you the differences I am talking about with respect to the inner gears that are going in these LSDs. I've already posted a 997 GT3 spide gear above. Below is the 996 gear. You can see that they used to be billet and properly ground, like a gear should be.
And here's the side gears, side by side. One is a used 996 gear and the other is a brand new 997 Cup side gear. In case it's not obvious, the lower gear is the 997.
The old style gears are definitely wearing better than the new cast gears they are using. I just put it out there because it's something you should consider for the future that you are going to need to service on these differentials. And it's not something that is resolved by upgrading to a Cup Car LSD. I've been getting asked a lot why someone should buy our $2700 LSD when they can get an 8 plate Cup Car LSD from Porsche for the same price. Well, this is the answer in pictures.
Something that would be worth exploring would be what exactly one gets if they order the side gear and spider gear service packs for a 996 LSD. If the old gears are what fall under that part number, it may be a cost effective way for people get the better gears in their LSD. But my gutt feeling on it is that like purchasing our gears separately, it's likely not cost effective and probably going to point people towards the direction of buying an all new LSD at the point that their spiders wear out.
Regards,
Matt
04-20-2010, 09:46 PM
#66
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WOW, the 997 LSD inner look really cheaply made compare with 996. That is too bad that Porsche fall into the same trap of cost saving by sacrificing quality. I heard that the new titanium center exhaust found on GT3 R and RS are cheaply made to save cost and it does not hold up to rigor of race and the damn thing has been blowing up. I feel better the fact that my ramps have been replaced with your beefy GT gears 
10-05-2010, 08:52 PM
#67
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Quick update. It's not a bad idea to change tranny oil after using the new LSD for couple months. This is what my drain plug look like after about 12 + track events with rebuild LSD. Still work perfectly 
10-05-2010, 09:41 PM
#68
Race Director
I ordered the Guard GT2 billet LSD and had it installed a few weeks back.
I tried it out 2 weeks ago.
WOW!
What a difference.
No more tail wag under braking and I could power out of corners like never before. Awesome. Worth every penny just for the safety in a straight line.
Matt, off topic question but can I have the 996 GT3 diff that I took off rebuilt and have it installed in my 2005 997S that doesn't have one?
I tried it out 2 weeks ago.
WOW!
What a difference.
No more tail wag under braking and I could power out of corners like never before. Awesome. Worth every penny just for the safety in a straight line.
Matt, off topic question but can I have the 996 GT3 diff that I took off rebuilt and have it installed in my 2005 997S that doesn't have one?
10-05-2010, 10:06 PM
#69
Suggest to change after the first 3-4 hard track days after initial install to get out the break-in material that has sheared off. I have changed my diff lube twice now in 10 track days since Guard install.
Another very happy customer of Guard and Matt. Superb parts, great people. The car hooks up like a monster and the RR tire doesn't wear twice as fast as LR.
PS- Johannes van Overbeek gave us a one hour chalk talk a few weeks back and I was amazed how often "lock the diff" and "get the diff locked" came out of his mouth as he described his technique to get around Laguna Seca. A fully functional and properly ramped LSD is critical for track rats!
Kudos again to Mr. Mikymu for his excellent thread on this subject
10-05-2010, 10:56 PM
#70
Rennlist Member
I've changed all oil after the first couple of track days and after the first 9 days. Form here on, I think I will change engine oil every 6-8 track days and 12-16 track days for trans oil. Seems like cheap insurance.
LSD is the only and last thing on my list.
Trying to get it done before VIR and Sebring the end of this month.
Not sure how it all works, but I think we will just be cheap and put the CUP stuff inside the stock housing and see what happens.
LSD is the only and last thing on my list.
Trying to get it done before VIR and Sebring the end of this month.
Not sure how it all works, but I think we will just be cheap and put the CUP stuff inside the stock housing and see what happens.
