Hi
i will be attending Roddisons and staying for a Curry, see you there, Mike
There is a lot of interest in this event, this comment came in this morning
’We have some unresolved issues with our own ND gearbox so we will be there’ G&C
This event is open to members and forum members from all areas.
https://www.mx5oc.co.uk/event/see-broken-inside-nd-mk4-gear-box/?instance_id=6879
Sorry guys family illness prevents me going. Thanks a lot for arranging and the open invite
Sorry you cannot make it, I will forward photos and summary It looks like being a good turn out, there is a lot of interest.
Hope you your family member returns to good health quickly
Hello Burton,
I and I’m sure others would be interested in the photo’s and summary, are you able to share them here?
Was there any video too?
Thanks
Ian
Firstly many thanks to Paul Roddison and Burton of Peaks & Pennines for arranging a very interesting evening looking into the failed Mk4 gearbox.
In addition to opening up a failed gearbox Paul also had a two pairs of failed gears. It was these failed gears which provided a good insight into the cause of the gearbox failures.
One gear in particular was a perfect example of gear tooth bending fatigue failure. The fracture face of two of the missing teeth showed classic high load fatigue crack “beach” marks which had emanated in the root, towards one end of the tooth, and then travelled in an arc into the tooth until final failure. In addition a number of the gear teeth which were still intact had visible fatigue cracks in the roots of the tooth again at one end.
From what I observed the cause of Paul Roddisons Mk4 gearboxes is clearly bending fatigue failure of the gears. This could be due to a design weakness of the gears themselves, incorrect gear material or heat treatment, poor manufacture or uneven tooth loading due to deflection of either the main shaft or layshaft. Which of these is the root cause would take further investigation.
I agree with Paul Roddison that the reduction in the final diff ratio when compared to the Mk3 does put a higher torque loading on the gearbox components. However the designer should have taken this into account. Automotive gearbox design is a “mature” industry with well proven design fomulas and I fail to understand how Mazda can get something like this so badly wrong.
Whilst at the moment in the UK it is mainly the Mk4s that have been raced which are suffering gearbox failures it is the nature of gear tooth bending fatigue that failures will occur in other less highly loaded gearboxes, it will just take longer to reach the point of failure.
Paul Robinson
Hello Paul & Burton
Thank you very much for organising another informative & interesting session.
Paul Robinson has accurately reported on the evening event.
The concerning news that a gentleman from Derbyshire, he was not present, had
suffered a broken Mk4 gear box at 1800 miles. Mazda UK were reluctant to honour
the warranty on the grounds that the car had been fitted with non standard front
brakes!
I had planned to purchase a MK4 2 litre next Spring & had a list of questions for
Paul Roddison to give advice on. However as I entered the garage a white MK3.75
caught my attention. A chat with Rodders, ensconced in the Recaro seat, saw me
back at 8.30 am Wednesday Oct 25 for a test drive.
I collect my White Sport Tech Recaro Friday Nov 3, my Black 2 litre MK3 Sport, is definitely
worth considering if anybody is in the market for a sensibly modified MK3; talk with Paul.
It would seem that just 30 Sport Tech Recaro’s were available in the UK all were Black
except for 1 White one. Info from www.roadster.blog
Keith
Many of the Recaros were white, that is not quite accurate info there were red and silver options also.
They were ordered as a batch (this combo being available in other markets but not the UK) and all (think 100) destined to go on to be come JOTA GT Sports edition that Lodge Garage was solely responsible with the Mazda & Jota partnership at the time. The uptake on that fabulous model did not go as well as it should (that is a really rare spec) and with the 25th anniversary coming these cars were released back into the dealer network and labeled Recaro.
Please dont let that take away from it, they are a great version of the mk3, rare and desirable so congrats on getting one. Had to drop it from the Special edition display earlier in the year as no-one came forward with one, but now we know!
Hello Iain
Thank you for the information, it would be interesting to find out how many other white Recaro’s
are on UK roads.
A little more info on my car; Roddison 175/180 bhp upgrade, Tein shocks/springs, hid’s (dipped beams),
all sensible modifications.
The car was offered with Willwood front brakes, Paul kindly replaced these with O/E calipers & pads.
I have no experience of Willwood brakes but to clear the front wheels the previous owner had fitted
spacers,I am not a fan of wheel spacers.
“Carbon fibre” subtle boot spoiler & front splitter, I am not absolutely sure about these body modifications.
First thing I will fit my set of 16 inch winter tyres/wheels.
Regards
Keith
Thanks again for your input during the TEK night.
Could you just explain something to me please, is the torque exerted on the gears within the gear box the same?
What I mean is when the car is in second for example is there more stress on this gear than say fourth?
Power is a direct function of Torque x RPM.
For a given power throughput, if you double the RPM, the Torque is reduced by a factor of two.
If you reduce the RPM by a factor of two, the Torque will double.
In simple terms, a gear that rotates faster will not have to deal with as much Torque.
What Rodders has said about the relatively tall rear axle ratio is very understandable.