MX-5 OC Forum

brgreen1:

Surely they would do a recall if it were a danger

What an interesting world it would be if our safety was car manufacturers top concern.

Truth is that if they were that worried about our safety, then the MX5 would probably never have been born.

Unless a manufacturer makes a feature of how safe a car is, it tends to be quite far down the list of prioritys....... Usually well below "How much profit can we make from it?"

Scotty B.

Jimbobsquarepants:

In the event of any substantial failure the casing are likely to split way before any wheels lock,

I hate to say it, But the Mk1 and 2's diff carrier is made of cast iron.

For those of you interested in this problem and how to minimize the chance of serious injury and very expensive further damage to your transmission driveline caused by a serious manufacturing/design defect regarding LSD type differentials fitted from 2003-present:

If you are worried about a potential £500-1200 repair bill coming your way, please have your rear axle oil drained and ask you mechanic to look for large (15mmx9mm) rectangular tabs made from hardened steel that will be stuck to your magnetic drain plug if partial failure of your LSD has already occured, if this is the case with your car please write to Mazda UK, Mazda Hiroshima, and VOSA here in the UK.

My concern for your safety is genuine, my concern for your wallet sincere, other people for some un-educated reason are trying to play this serious problem down, I urge you to use your own judgement in this instance.

Regards, Dr. Eunos

Dr. Eunos

Jimbobsquarepants:

Agreed but the casings are not, in the event of a total failure in which debris became trapped between the crown wheel the weakest point would be the casing holding the pinion shaft against the crown wheel casing.

That's the bit I'm talking about.

The rear casing of a Mk1 and 2 diff is aluminium (I think the Mk3 has an all alloy design), But the front half it cast iron and it's this half that hold the crown wheel and input pinion together. The rear casing is just an alloy cover with cast in mounting arms and the drive shafts oil seals built in.

I know this as I have a complete Torsen LSD diff (Minus the rear cover) waiting for me to fit in my car. The pinion, diff and casing is together in one unit and it weighs a fr1ggin' ton.

If the diff did get jammed I'm pretty sure that the weakest link would be the friction between tyre and road, And I'm pretty sure this would happen long before the diff got anywhere near popping it's casing.

Think about it this way, MX5's with turbo or supercharger can quite easily overpowered the friction available between the tyre and road by just stamping on the loud pedal. 99.999% of the time the tyres let go before anything gets broken. That 0.001% is when you manage to snap one of the aluminium mounting arms off the diff, It's not the crown wheel or pinion stripping teeth and it's not the cast iron casings splitting.

Actually, Jimbob that is very much the strongest point in the diff casing and the highest point-loading occurs in the casing where the pinion shaft enters the front of the diff.

Mr. Reman, hello by the way, do you agree that given the right circumstances (wet road, bend, lightly loaded inside wheel, half worn tyres) the rear wheels could lock if these hardened steel tabs get jammed between the crown wheel and pinion?

The other factor is that if I heared a sudden bang in the back of my car, my instinct would be to put the clutch in..........which would be pretty much the worst thing to do if I wanted to stay on the road...

Do you remember the story `The Kings New Clothes`? -Thats how I feel about this problem it would be good to know someone else can see the potential catastrophic results of this definate design/manufacturing defect.

That is why I`m on here at 7AM on a Sunday morning to underline the danger to you.

Dr. Eunos

 Hi all,

As an insurance engineer,and graduate of the institute of Automotive engineering assessors,please head Mr eunos comments.

1. This is a latent defect that can only be a manufacturing fault,as such you are covered under the sale of good act.*this under current legislation is 6 years,but could be argued ,how long would you expect the diff to last?i would suggest as long as the car,a 100 thousand miles as a minimum.

2. Why are the tabs there?if two have snapped off,why have they snapped?what was the cause?and you now have twice the forces on the remaining tabs.

3.What could happen next?nothing or something...which would you prefer?and which is more likely?yes you could probably drive another 100 thousand miles and nothing happen,then again something might,diffs work on fine tolerances,and you usually have to set the back lash up,which is the tolerance between the crown and pinion.The likely hood of the tab getting between these is plausable to high,they would more than likely crush the tab,and spit it out, as there made of differing materials,and would doubt would jam,unless their of a harder material.So all sounds good now eh?whats holding the diff together?i'm not too familiar with the diffs on mx5's...but the thought of anything being loose is never good.If your car locks its diff and sends you into a bus que ,how would you feel...?

4.what do you do?as a lay person, you are not in position to offer a opinion,as Mr eunos has mentioned,get someone who is,both the people he has mentioned are easily experts in there field,and recognised.Alternatively ,get the diff inspected by an independant engineer.(and i dont mean jo bloggs from a garage)refer to the Institute of the Motor Industry,or the Institute of Automotive Engineering Assessors in litchfield.

5.Sort the car first,make sure you get the diff inspected,and then take the relevant information to Mazda uk,make them aware you are a member on forums.Bad press is never good...Also as Mr eunos has said Mazda in japan as well,if a manufacturer,does not take action to a problem reported that could lead to death,its classified as corporate manslaughter..hence all the very recent recalls with toyota.And let vosa now.

Hope that assist all,if anyone has any queiries on needs help and advice give me a shout.

regards

Tim

sidewayssam:

 Hi all,

As an insurance engineer,and graduate of the institute of Automotive engineering assessors,please head Mr eunos comments.

1. This is a latent defect that can only be a manufacturing fault,as such you are covered under the sale of good act.*this under current legislation is 6 years,but could be argued ,how long would you expect the diff to last?i would suggest as long as the car,a 100 thousand miles as a minimum.

2. Why are the tabs there?if two have snapped off,why have they snapped?what was the cause?and you now have twice the forces on the remaining tabs.

3.What could happen next?nothing or something...which would you prefer?and which is more likely?yes you could probably drive another 100 thousand miles and nothing happen,then again something might,diffs work on fine tolerances,and you usually have to set the back lash up,which is the tolerance between the crown and pinion.The likely hood of the tab getting between these is plausable to high,they would more than likely crush the tab,and spit it out, as there made of differing materials,and would doubt would jam,unless their of a harder material.So all sounds good now eh?whats holding the diff together?i'm not too familiar with the diffs on mx5's...but the thought of anything being loose is never good.If your car locks its diff and sends you into a bus que ,how would you feel...?

4.what do you do?as a lay person, you are not in position to offer a opinion,as Mr eunos has mentioned,get someone who is,both the people he has mentioned are easily experts in there field,and recognised.Alternatively ,get the diff inspected by an independant engineer.(and i dont mean jo bloggs from a garage)refer to the Institute of the Motor Industry,or the Institute of Automotive Engineering Assessors in litchfield.

5.Sort the car first,make sure you get the diff inspected,and then take the relevant information to Mazda uk,make them aware you are a member on forums.Bad press is never good...Also as Mr eunos has said Mazda in japan as well,if a manufacturer,does not take action to a problem reported that could lead to death,its classified as corporate manslaughter..hence all the very recent recalls with toyota.And let vosa now.

Hope that assist all,if anyone has any queiries on needs help and advice give me a shout.

 

regards

Tim

Hooray! Someone else recognises the dangerous aspect of this defect

Tim these tabs are part of the stator element  and are actually made of hardened steel. They do not get squashed if they go between the crownwheel and pinion, they smash the teeth off the pinion generally, it is only a matter of time in my opinion, until an axle locks solid with potentially catastrophic and injurous results. These tabs locate the stator plate of which there are two either side of the output drives there should be 4 of these tabs (locating lugs) in each of the two stators which are dished in at their outer circumference and offer resistance to the over speeding wheel via a segmented sintered metallic friction surface being clamped against the either output side of the differential which is chamfered to the same angle of the dishing of the stator plate, clamping force is via a worm-gear arrangement similar to a TorSen set-up.

Robbie Roadster, this clubs` `technical Consultant` did have some photographs of the shattered internals of a diff which had had these tabs/lugs jam inbetween the crownwheel and pinion and they also showed where the tabs had sheared off from. They very clearly showed that the very design and manufacturing of these stators are at fault as you could clearly see a nasty 90 degree `stress-raiser` at each corner of where the tabs had been cut into the stator plates during their manufacture. RR felt he needed to remove the photos from public view `for potential legal reasons,` following my initial voicing of serious concern over the problem.

Thanks for recognising the danger and responding to the post.

Dr. Eunos

 your welcome,and if you have any photos of the diff,send me a private message and i will give you my email address.

regards

Tim

sidewayssam:

 your welcome,and if you have any photos of the diff,send me a private message and i will give you my email address.

 

regards

Tim

 

Cheers Tim, I requested copies of the photos to be emailed to myself this morning from RR but as yet nothing forcoming. It is of course his perogative as to whether he chooses to send them across or not.

Hopefuly we can get some action from Mazda without having to wait for photos of someone elses total diff failure caused by this defect in the meantime.

Dr. Eunos

 Im glad I've found this thread

I'm on my second diff now and this one is doing better but the tabs are still braking off even when I change the diff oil every 5k or every two track days.

The tabs from the first Diff

I swap this for a another second had diff I bought and took the old one to bits to look for what damage I had. since mine had start to make a fair amount of noise

all the damage was on the crown wheel

 Ollie, you have PM

Dr. Eunos

 thats fab,do you any pictures of the diff or crown wheel?the more info we have and photos the better!if anyone else out there has any please put them up,or mail them to me directly,pm me and i will give you my email .

many thanks

Tim

 Hi Guys ive got pretty busy weekend but will try and get images of the diff for you as soon as my work load has buggered off.  I will post the images i have on my photo bucket

 Hi Ollie, sadly this is a different type of diff to the one in question- it doesn`t seem to have the problematic dished friction plates where the lugs we are talking about would have snapped off from.

Thanks for the photos though and better luck with your next diff

If anyone else suffers diff failure of an LSD and the casing is opened somewhere other than a franchised Mazda UK dealer please do send your photos in. We suspect Mazda are very well aware of the problem and are only really interested in helping owners of cars whose vehicles are within warranty.

Owners of older vehicles with this problem who still have thier vehicles serviced within the dealer network will in all probability not be told of large bits of hardened steel that may have been stuck to the magnetic drain plug while the vehicles are serviced.

Don`t forget, when one or more of these tags has snapped off , the LSD action of the diff will have been significantly weakened and far more prone to more of these tags (8 in total) cracking off the plate and possibly jamming and causing total failure of your diff and a possible accident.

I would very strongly advise owners to be aware of a potential cause of the actual fracture of these badly designed components, could possibly be due to rear and handbrake testing rollers at MOT time. Owners should inform the MOT tester that their car has a limited slip diff (with a known weakness) and request that brake testing rollers should not be used on the rear of thier vehicle.

In reality a differential should easily last for at least 100,000 miles on a road car..................................

Dr. Eunos

taff eunos:

 Hi Ollie, sadly this is a different type of diff to the one in question- it doesn`t seem to have the problematic dished friction plates where the lugs we are talking about would have snapped off from.

That is the same type of diff, it has springs inbetween the sun gears! The taper rings are inside the differential element of the assembly...

taff eunos:

 ...clamping force is via a worm-gear arrangement similar to a TorSen set-up.

"Clamping force" is generated by friction between the taper ring and the sun gear, the springs help with this. This type of diff has no worm gear.