Good day Taff
These look familiar.Could even be mine?
All the best
Denzybaby
Hi denzibaby, quite correct they are your bits of carnage and shrapnel- Im just really, really, really glad I am fortunate not to have one of these awful contraptions in my diff casing
Hi Tony,
I’ve just had a similar reply so it looks like determining LSD with regard to RBT is being left to the individual MOT tester. I’m not sure why they commented about the LSD being not standard to this model though. If they don’t involve themselves in recording LSD then why comment, and who has given them such wrong information? Strange.
"FREEDOM OF INFORMATION ACT 2000<o:p></o:p>
<o:p> </o:p>
I refer to your e-mail of <st1:date year=“2011” day=“2” month=“11”>2nd November 2011</st1:date> in which you asked whether our records show that your vehicle is fitted with a Limited Slip Differential.<o:p></o:p>
<o:p> </o:p>
The Vehicle and Operator Services Agency does not hold information in relation to the fitment of a Limited Slip Differential (LSD) to your vehicle. The records held relate to make and model variations, and it is our understanding that the fitment of a Limited Slip Differential is not standard to this model. <o:p></o:p>
<o:p> </o:p>
If you have any queries about this letter, please contact us, quoting reference…"
Hi Taff, all,
Thanks for your thoughts, that’s how I too would feel if I had an affected car.
So, is this device elegantly simple, or simply crude? The first I think, but something may have gone wrong in design and/or production with some of those fitted to Mk2.5 models at least.
So far, Mk3s do not seem to be affected. It may be a similar unit but not the same as I think the half shafts are a different size apart from anything else. Whether the problem was found and Mk3 diffs changed we don’t know. In a way it’s worse for Mk3 owners, not knowing if theirs will pack up sooner or later as well. Who’d want to buy a brand new MX5 with this hanging over them?
I see Mazda and GKN are using this design in the Mazda 3 MPS as well,
http://www.gkndriveline.com/drivelinecms/opencms/en/media-centre/news/gkn-news/article_0031.html
They would do well to make clear what has happened with these failed MX5 Mk2.5 cars rather than having this shadow hanging over their newer releases.
I’m a new member of this club but I strongly suggest the Club takes this matter up with Mazda and GKN now on behalf of all affected owners. Send them a letter and publish it here openly. Let them explain what has happened and clear the air. Make this thread more prominent on the site, give it its own section and heading. I’m sure Taff will be only too pleased to let them examine the parts he has but I suspect they know already.
At least two of my MOT’s have been carried out by Mazda Dealers who both said it was their standard practice to use a roller brake tester on MX5’s. They did not even raise the issue of LSD’s.
Worrying.
Hi Paul,
I don’t think RBT has anything to do with these failures. Clarification from a technical expert at Mazda or GKN would be welcome.
Here is Mazda’s description of the Super LSD taken from their technical guide.
Mazda refer to the sun gears as side gears and the planet gears as pinion gears
Outline
• The super-LSD is a torque-sensing type that provides improved driving stability due to the following characteristics:
- - Low torque bias ratio provides improved controllability (torque bias ratio: 2.0)
- - Creation of initial torque provides improved starting from a standstill and acceleration/deceleration response, and driving straight-ahead (initial torque: 49 N·m {5.0 kgf·m, 36 ft·lbf})
- - Simplified construction provides weight reduction
• The gear case component of the super-LSD cannot be disassembled.
Construction
• Inside the super-LSD, taper rings that are fixed to the differential gear case have been placed between the differential gear case and the side gears. Additionally, a cone is provided around the outer surface of the side gear.
• Springs and retainers are positioned between the right and left side gears to provide initial torque to the taper rings.
Operation
Straight ahead driving
• When driving straight, the right and left side gears rotate at the same speed, and the pinion and side gears rotate together with the differential gear case. Input force from the ring gear is transmitted to the pinion gears via the gear case and to the drive shaft via the side gears. Due to this, a speed difference between right and left in the differential does not occur.
Differential operation
• If the rotation speed between the right and left wheels becomes different (during normal driving), the pinion gears rotate together while revolving around the center axle of the drive shaft, thereby absorbing the difference in rotation speed. This mechanism serves as a differential.
Limited-slip operation
• If the differential encounters a condition requiring limited-slip control such as wheel spin, thrust force acts on the side gears due to the reaction force from the meshing of the pinion and side gears. This thrust force presses the side gears against the taper ring, generating friction between the side gear cone and the taper ring and reducing the torque of the slipping wheel. The reduced torque is transmitted without change to the wheel with higher traction, and the limited slip differential function is provided. The torque transmitted to the wheel with higher traction is proportionate to the input torque of the ring gear.
Thanks Robbie, that confirms the working but it would be good to get Mazda or GKN to confirm,
-
whether or not it can be RBT in the same way as a regular diff and
-
to explain what has happened to those Mk2.5 diffs, what they propose to do about it, and
-
whether Mk3s have a different or modified version to prevent similar failure.
Frankly, I am apalled by their lack of communication. There have been 11000+ viewings of this thread and posts on several other forum from owners in others countries so I’m sure they know about it. I’ve recently bought my Mk3 car and think it is awful owners are left with this hanging over them not to mention the effect on resale values.
Rich,
Speaking as a MK2.5 owner who has recently found chunks of metal in my LSD, I must say that I do not think any company (Mazda nor diff supplier) owes me an explation, nor compensation, nor replacement parts.
I see this as a shortfall in my expectations, but I see this as “legally understandable” wear and tear. All of the MK2.5s are at least 6 years old now, and despite the safety related conversations of the first 8 pages of this thread, I do not consider my car to be dangerous. The LSD still performs as an LSD, despite the metal chunk (only one in my case) coming off, and having held the offending chunk in my hand, I cannot see any way at all that could possibly be strong enough to lock the diff and cause loss of control.
I don’t see this as an endemic design fault, I think too few cars suffer for that. It is possibly a manufacturing fault in a select batch of cars, but I am very confident Mazda (as any manufacturer fearful of law suits) will have destruction tested the diff before specifying it for the cars.
It may be akin to burying my head in the sand, but I am going to happily continue to drive my car hard, on track, with this diff. If the LSD part fails, or worse, then I shall likely go the Quaife route.
Just my tuppence worth of thoughts.
Martin.
Really? Does anybody really know that?
Why then, are LSDs not supposed to be RBT’d. When I took mine for it’s MOT it quite clearly stated on the pre-MOT checklist that LSDs were not to be RBT’d.
I believe testers do not notice that or are unaware these cars have LSDs - you have to tell them yourdelf!
See my posts a few pages back.
Hi Martin,
It’s good to hear you’re not particularly disappointed and I agree with some of what you say. My points 1) and 3) are of personal interest as a Mk3 owner but answers to 2) would help understand what has happened, re-assure me with regard to the quality of the product, and may help others. For example, if I had a full service history 40K mile Mk2.5 with this problem I would feel disappointed and hope for some help from Mazda. You may consider a higher mileage car bought for track days differently.
Look at your own posts in this thread and we see that first you heard about the problem and a week later you drained the diff and actually had the problem. How coincidental is that if it is not a common problem? You found only1 piece but others may have been removed before, or are lying in other parts of the case, and others may be broken and rattling around as we see from the burr marks on the fractures in Taff’s pictures. If you are sideways in a corner and a piece goes through the gears, either blasting round the track or meandering across the Pennines on a sunny afternoon with a loved one, there is a good chance the rear wheels will slide. Just my thoughts of course.
Hi Phil,
I don’t think there will be a problem if the prop is not under load. That’s just my opinion from how I understand this diff to work.
I agree that, going by their own instructions, MOT testers should not be testing these diffs on a RBT as they are an LSD. It would be helpful if Mazda or GKN told us and them if they can be tested without harm if that is the case. That might lead to an exemption, but either way VOSA rules need revising or enforcing.
The reasons for the rule against RBT of LSD may be many and it may simply be a catch-all rule to avoid problems. I’m thinking of some LSD that may be damaged by overheating their plates, transfer of torque to the other wheel thus rendering the brake test results inaccurate, or simply throwing the car off the rollers with ensuing dangers. I don’t think any of that would happen with this LSD - but - I am not an expert and do not know 100% and cannot see why Mazda or GKN do not put this to bed sharpish.
Earlier when I said that at least two of my MOT’s were carried out by Mazda Dealers, I omitted to say that on one of the MOT forms is the warning about LSD’s and not doing a RBT. It also says the tester should verify whether the car has an LSD or not.
One of these dealers also put two chinese import tyres on the back end when I first had the car which made it lethal in the wet. Soon had those off.
Car companies do google themselves, but the only way to trigger a recall is through dealer reported faults. Talk on the internet is worth nothing - every failed part should be taken to a dealer and you should make sure they report it back to Mazda with the VIN of the vehicle it came from. Mazda will have the batch data and will be able to recall cars affected, but only if they have enough evidence via their own data that something needs to be done.
I’ve seen dealer reported fault data from other manufacturers, and it does get back to the people who made the car, and they do have to react to it.
Posts on the internet will be largely ignored because the source is so untrustworthy (not believing this statement actually proves it).
No manufacture destruction tests anything (except for whole cars in crash tests). What happens is a durability target is selected (100,000 miles, 2,000 full throttle standing starts, -40 degree transmission shock load, constant 1g cornering for as long as the fuel tank size will allow, or anything else the engineers can think of - this was my job for a while), then a series of tests devised to replicated that target, then parts are tested and at the end of the test inspected. This testing will be repeated every time there is a design change or new supplier is used. This is how all car manufacturers operate. Every part could be on the point of failing at the end of the test and no one would ever know - they test to “reasonable” targets and sometimes the real word isn’t “reasonable”.
Companies with a reputation for reliability use the same process, they just have tougher targets than they need to satisfy legal requirements.
Hello Rich
I am just going by my own experience. I got my car at 23k miles so I would have thought it unlikely that the diff oil was ever changed from new up to that point.
When I first read about this problem I thought right change the diff oil and check for the broken tabs - I thourily searched the magnetic drain plug, the drain tray and stuck my finger in the hole - there were none, only paste which you would expect.
When I took it for the MOT I made a point of looking at the pre-MOT checklist and it definitely made a reference to LSDs. The tester would have RBT tested if I hadn’t pointed this out and asked for it to be inertia tested. He had no problem with this and drove the car up and down his yard several times tesing footbrake and handbrake with the meter and for pull left or right. It’s had 2 MOTs like that now, what went before I don’t know. Maybe I’ve just been lucky.
The other thing is, is that I’m a boring old sod and don’t thrash my cars, do handbrake turns or something they call today - drifting!
It is still not certain that Mk3s haven’t got this issue, perhaps as time goes on and more and more of them get several MOTs more will come to light.
As for Mazda reacting to this problem - well 
I do agree, however I also see Mazda’s “side” to this. A lot of our cars are outside of the dealer network now and onto 3rd/4th owners. If I were to take my 2003 99k mile car in to the dealer, I would get the polite version of “tough luck fella, its an old, leggy car that may have been abused repeatedly” response. Thus, I don’t take it to a dealer, thus the dealer base possibly remain blissfully aware of the problem. So from Mazda’s point of view, a 40k mile FSH MK2.5 comes in with a diff leaking metal parts and the first thoughts have got to be one-off, unusual, must have been treated badly by the owner. Catch 22 I guess.
I may be old fashioned in my views, but I consider cars to be hugely complex machines made up of 1,000s of parts. To expect them to remain failure free for months, years, decades is unrealistic.
This is part of the reason why I was able to buy my Sport for £2k, but it would cost £20k to buy the equivalent brand new version. Piece of mind is expensive.
Good point. I suppose what I was meaning to say was whilst the problem may or may not be common, negative symptoms (total failure, locked diffs, losses of control) as a result of this are almost unheard of. I found the piece of metal because I read this thread and went looking for it. Without reading the thread, I doubt I would have bothered changing the diff oil yet, and I certainly would not have gone looking for metal in the diff. I imagine there may be many owners driving around happily unaware.
Martin.
CM, thanks for the explanation. Enlightening, and whilst I imagined this was the case, I was not aware of durability testing.
It does beg the question though to me, of what the underlying issue may be. The diffs must have passed this durability testing.
I would not consider the MX5 to be a particularly torquey car, certainly not compared to the turbocharged MPS (though of course that torque is split to all 4 wheels) cars that has been suggested have the same diff, so I wonder if we can assume the diff is strong enough. I wonder if it is an overheating type of issue, with cars not getting the diff oil changed regularly enough?
Martin
Good advice Captain Muppet. It’s down to each one of us to complain with a proper paper trail when there is a problem. Things will not be sorted or improved if we are apathetic. The only thing I would disagree with is that the posts here are worth nothing. The world has changed with the internet and manufacturers must keep up and improve their communication. If I were a manufacturer I would not like to log on and see these posts.
Yes, all agreed Martin, buy it for what it is and use it accordingly, can’t fault your logic, have fun! :)
The Failure Mode Effects Analysis will have predicted the failure. FMEAs are basically a list of all features on all components complete with an exhaustive list of how they can fail. This then drives the testing required to avoid failures in service. If the FMEA is done well the number of occurences of failures noticed by customers will be tiny - and without every instance being reported to Mazda no one knows how big or small a problem this actually is.
Assuming the parts sailed through the initial validation phase there are still things that could affect the durability of tyhe part. A bad batch from a supplier, or a change in assembly technique by a supplier, or a silly brake test for MOTs in a country 5,000 miles away that shouldn’t be applied anyway, or a combination of lots of unrelated factors. Combine a bad batch of material material from the tier 3 supplier, tool wear and iffy heat treatment from the tier 2 supplier, freak abusive assembly process at the tier 1, then infrequent servicing by the third owner of the car and an MOT brake test at sub-zero temperatures and bingo - some bits of metal in the bottom of your drain tray.
Or maybe the chances of a heavy bit of metal in a diff casing getting scooped up in to one of the gears in such a way as to cause an incident the customer would notice are so tiny that the failure is statistically insignificant, so it doesn’t matter.
Without accurate recording of failures through the proper channels no one will know.