LSD rebuild question
01-20-2010, 03:47 PM
#31
Instructor
I just spent about two hours preparing a long response to Matt Monson of GT but it got sucked up/lost by this system and I don't have the energy to do it all again so I will attempt to shorten and summarize but the story may not "flow" as well as it did before. Sorry.
My transmission did not fail. My LSD failed thru self destruction.
Jerry Woods Enterprises (both Jerry and Rich) are well aware of all the circumstances in this case and anyone can call them to get the story as they saw it first hand. Their diagnosis was a destructive incompatibility between the GT friction discs and the floater discs. Clearly the floater discs were substantially and destructively ground away by the friction discs leaving metal slurry throughout the tranny. Other than that, the rest of the LSD remained intact and perfectly operable.
GT had received my LSD beforehand, had measured it, tested it, rebuilt it, etc. and had chosen to only replace the friction discs and reuse the floater discs. Perhaps that was a bad call and the fatal flaw but that was one of their making and no one else's. My decision to use GT to rebuild my LSD was based on their excellent reputation and several emails and phone calls beforehand. I was never told nor did I have the impression that the use of GT friction discs would be an experiment nor did I have any reason to believe there might be substantial failure.
When the dust settled, GT had an opportunity to blame Jerry Woods (JWE) for an incorrect LSD installation and of course they didn't do so, particularly considering JWE is a recognized expert in LSD and transmission rebuilding and installation. Instead GT chose to contend there was inferior metallurgy in some 40/40 LSDs and that must have been the culprit. From GT's view it was my bad luck and my mistake.
My contention is that I paid money to get expert parts, service and advice from GT and they failed me. GT could not bring themselves to admit fault, particularly considering that I had only paid them a few hundred dollars overall but the damage done was several thousand dollars. Presumably they had insurance to cover such a contingency but that's another story.
I certainly understand and appreciate that Mr. Monson wants to stand behind his products and his company's good name. I applaud him for that. However, I have now made people aware that there can be an expensive failure in using GT friction discs with some 40/40 LSDs. Exactly why that is the case or exactly when that may happen I don't know, but as a expert in the LSD industry, GT should be expected to know. In the future, just how GT chooses to use that information and how rennlist readers choose to use that information remains to be seen. Frankly I'm surprised to hear that Mr. Munson wasn't made aware of this catastrophic failure in my case as it was a "big deal" at the time.
From what I've seen and been told, there is no reason to think that my 40/40 LSD failure with the GT friction discs is some kind of unique freak case which likely cannot ever happen again. That's why people should be aware and forewarned.
I stand behind my story but people can, and will make up their own minds about what happened, may have happened, etc. Furthermore. I have taken the unusual step/liberty of attaching my name and telephone number if anyone wants to discuss this on a more personal basis.
As far as I'm concerned the matter is settled. I've made my point and stated my case. Yes, I have some residual hard feelings toward the former owners of GT but let's get on with life. I'm done.
Cheers,
Warren Gardner
510-449-9177
My transmission did not fail. My LSD failed thru self destruction.
Jerry Woods Enterprises (both Jerry and Rich) are well aware of all the circumstances in this case and anyone can call them to get the story as they saw it first hand. Their diagnosis was a destructive incompatibility between the GT friction discs and the floater discs. Clearly the floater discs were substantially and destructively ground away by the friction discs leaving metal slurry throughout the tranny. Other than that, the rest of the LSD remained intact and perfectly operable.
GT had received my LSD beforehand, had measured it, tested it, rebuilt it, etc. and had chosen to only replace the friction discs and reuse the floater discs. Perhaps that was a bad call and the fatal flaw but that was one of their making and no one else's. My decision to use GT to rebuild my LSD was based on their excellent reputation and several emails and phone calls beforehand. I was never told nor did I have the impression that the use of GT friction discs would be an experiment nor did I have any reason to believe there might be substantial failure.
When the dust settled, GT had an opportunity to blame Jerry Woods (JWE) for an incorrect LSD installation and of course they didn't do so, particularly considering JWE is a recognized expert in LSD and transmission rebuilding and installation. Instead GT chose to contend there was inferior metallurgy in some 40/40 LSDs and that must have been the culprit. From GT's view it was my bad luck and my mistake.
My contention is that I paid money to get expert parts, service and advice from GT and they failed me. GT could not bring themselves to admit fault, particularly considering that I had only paid them a few hundred dollars overall but the damage done was several thousand dollars. Presumably they had insurance to cover such a contingency but that's another story.
I certainly understand and appreciate that Mr. Monson wants to stand behind his products and his company's good name. I applaud him for that. However, I have now made people aware that there can be an expensive failure in using GT friction discs with some 40/40 LSDs. Exactly why that is the case or exactly when that may happen I don't know, but as a expert in the LSD industry, GT should be expected to know. In the future, just how GT chooses to use that information and how rennlist readers choose to use that information remains to be seen. Frankly I'm surprised to hear that Mr. Munson wasn't made aware of this catastrophic failure in my case as it was a "big deal" at the time.
From what I've seen and been told, there is no reason to think that my 40/40 LSD failure with the GT friction discs is some kind of unique freak case which likely cannot ever happen again. That's why people should be aware and forewarned.
I stand behind my story but people can, and will make up their own minds about what happened, may have happened, etc. Furthermore. I have taken the unusual step/liberty of attaching my name and telephone number if anyone wants to discuss this on a more personal basis.
As far as I'm concerned the matter is settled. I've made my point and stated my case. Yes, I have some residual hard feelings toward the former owners of GT but let's get on with life. I'm done.
Cheers,
Warren Gardner
510-449-9177
Last edited by Blu RS; 01-20-2010 at 04:19 PM.
01-20-2010, 05:03 PM
#32
TR-6 It would seem that this thread has gone a little sideways on you here, so I will try to help you out here first. No you do not need to worry about driving your car on the track with a LSD that may or may not be worn out. I do agree with Geoffrey completely with regard to the fact that there is a caveat to this, that being, so long as the plates internal, as well as the cross pins have not fractured or broken. In relation to this I have not seen fractured plated in quite some time, although it does occasionally occur, and the Porsche OEM Cross Pins, while also shown to fail from time to time, will have made such a noise, that I doubt you would be experiencing this problem. So all and all, I would not worry about putting your car onto the track.
In reference to your car pulling to one side or the other under acceleration, there are several possible reasons why this might happen, but certainly the differential is a possible culprit for this symptom. When you differential plates begin wearing out your car can experience uneven lock up internal to the LSD. What you feel as pull to one direction or the other inside the car is actually one wheel slipping away from the other inside of the differential, which should not happen with a fully functional LSD.
I would go have some fun at the track and pull your differential out later and inspect it. You do not have to worry about resetting the ring and pinion unless you decide to change your differential out with another unit. There is no such thing as a plug and play LSD. You ALWAYS need to reset the ring and pinion if you decide to change it out with another unit. However if you simply rebuild your current LSD, you should have no issues with reinstallation, provided that the ring and pinion was set up correctly the first time around.
There are always plusses and minuses to every choice that we make with regard to upgrading from one product to another. LSD selection is no different. Due to the precise nature of these differentials, I would recommend that if you do decide to have yours rebuilt, that you either use the OEM rebuild parts, or have your differential plates completely replaced, not just the friction plates. I would also recommend that you try to maintain a similar clutch plate count and preload to that of the stock unit.
As I have no intention of getting in the middle of things here Warren with relation to your unfortunate experience with the aftermarket plates you mentioned, I will only add this thought. I believe that in your case, your problems might have been avoided, if #1 all of the plates would have been replaced (not just the friction plates), and number two, if you would have changed out the oil after initial break-in. I am sorry to hear about your failure, no one likes to see this happen.
OEM and most aftermarket differentials, do require the friction plates to be broken-in and mated to their respective plane plates, this is a very easy operation, but is often overlooked. Once this process has been done, you can expect that there will be some material integrated into the oil. This is not especially good for your gearbox's bearings, and should be removed. From that point forward, I would heed the advice given here by Mr. Monson. While this is certainly not the case with everyone, transaxle fluid changes are very often over looked. This is important maintenance item that should be addressed on a annual basis for street cars and certainly more often for racing applications. The expense of having a gearbox rebuilt is by far more then the cost of a little preventative maintenance.
I hope that this helps,
Erik Johnson
GBox Performance Transaxles
(303) 440-8899 work
(303) 895-4828 cell
In reference to your car pulling to one side or the other under acceleration, there are several possible reasons why this might happen, but certainly the differential is a possible culprit for this symptom. When you differential plates begin wearing out your car can experience uneven lock up internal to the LSD. What you feel as pull to one direction or the other inside the car is actually one wheel slipping away from the other inside of the differential, which should not happen with a fully functional LSD.
I would go have some fun at the track and pull your differential out later and inspect it. You do not have to worry about resetting the ring and pinion unless you decide to change your differential out with another unit. There is no such thing as a plug and play LSD. You ALWAYS need to reset the ring and pinion if you decide to change it out with another unit. However if you simply rebuild your current LSD, you should have no issues with reinstallation, provided that the ring and pinion was set up correctly the first time around.
There are always plusses and minuses to every choice that we make with regard to upgrading from one product to another. LSD selection is no different. Due to the precise nature of these differentials, I would recommend that if you do decide to have yours rebuilt, that you either use the OEM rebuild parts, or have your differential plates completely replaced, not just the friction plates. I would also recommend that you try to maintain a similar clutch plate count and preload to that of the stock unit.
As I have no intention of getting in the middle of things here Warren with relation to your unfortunate experience with the aftermarket plates you mentioned, I will only add this thought. I believe that in your case, your problems might have been avoided, if #1 all of the plates would have been replaced (not just the friction plates), and number two, if you would have changed out the oil after initial break-in. I am sorry to hear about your failure, no one likes to see this happen.
OEM and most aftermarket differentials, do require the friction plates to be broken-in and mated to their respective plane plates, this is a very easy operation, but is often overlooked. Once this process has been done, you can expect that there will be some material integrated into the oil. This is not especially good for your gearbox's bearings, and should be removed. From that point forward, I would heed the advice given here by Mr. Monson. While this is certainly not the case with everyone, transaxle fluid changes are very often over looked. This is important maintenance item that should be addressed on a annual basis for street cars and certainly more often for racing applications. The expense of having a gearbox rebuilt is by far more then the cost of a little preventative maintenance.
I hope that this helps,
Erik Johnson
GBox Performance Transaxles
(303) 440-8899 work
(303) 895-4828 cell
01-20-2010, 07:05 PM
#33
Nordschleife Master
Their diagnosis was a destructive incompatibility between the GT friction discs and the floater discs. Clearly the floater discs were substantially and destructively ground away by the friction discs leaving metal slurry throughout the tranny. Other than that, the rest of the LSD remained intact and perfectly operable.
Right here is the root of the issue and something I will get behind 100%. For several years when I have needed parts for rebuilding an LSD, Paul Guard always told me that you have to use GT plain plates (aka floater discs) with GT friction discs. The old 20 year old factory plain plates are definitely not of the same hardness or alloy that is used today. Now your story makes total sense to me and I have no disagreement with the basis of the failure. However, I've got to tell you that I am at a loss. I don't know how an LSD that went through Paul Guard's shop ever had factory plain plates put back into. I can also tell you that no ZF LSD that ever comes through my shop will be rebuilt with a mix of GT and OEM parts because they are not compatible. This is something that I am well aware of and agree with.
Please understand, my post was never meant as an attack on you nor to call you some sort of liar. Furthermore, I never thought you made up your story nor that your failure was fabricated. What I had a problem with was your universal claim that GT parts are incompatible with all G50 ZF LSDs. I stand behind that disagreement, with the caveat that, as outlined above, you MUST use GT friction discs and plain plates together and not attempt to reuse or substitute Porsche factory plates. That's what happens when a differential comes through my facility.
Regards,
Matt Monson (not Munson)
Guard Transmission LLC
303-530-1094
01-21-2010, 12:14 PM
#34
Warren,
Thanks for sharing your experience in such a well documented fashion, I'm sure it will be of help when my LSD is up for reconditioning.
Matt,
Thank you for the refreshingly mature attitude in representing your company on here, I think many performance vendors active in online communities can take an example.
Rgds,
Harald
Thanks for sharing your experience in such a well documented fashion, I'm sure it will be of help when my LSD is up for reconditioning.
Matt,
Thank you for the refreshingly mature attitude in representing your company on here, I think many performance vendors active in online communities can take an example.
Rgds,
Harald
