- My model of MX-5 is: 2014, 22K, full service history__
__ - I’m looking for technical help or recommendations on: the rear diff noise, I think after about 50 miles but not all the time advise please, cheers MH__
First step would be to change the diff oil and examine what comes out.
There was a tech service bulletin from Mazda regarding earlier 2006 -2013 cars regarding excessive use of lapping paste during diff assembly which could cause wear in the crown wheel and pinion. This was rectified on cars built after May 29 2013.
There is also a chance of drive tabs on the lsd clutches breaking.
If the oil has never been changed then you would expect it to be black with a fair amount of magnetic paste on the drain plug magnet. Any other solids or fragments may tell a story.
The diff was slightly underfilled from the factory and a fluid change will raise that level slightly which could help.
Excellent !! Thank you for the info. It’s has a years Mazda grantee so I will get onto the dealer straight away
Thank you again MH
roof up or down.
don’t rule out the drain tubes
Hi Guys. Just to let you know the diff oil was changed and noise has gone. The dealer said some owner skip having the oil changed as it is an expensive oil. The oil in mine may have never been change as it’s a low miler but six year old so passed it’s sell by date.
Thank you again for your advice and putting me on the right track!
I was told change the diff oil as regular as you change the engine oil, especially if you use the car for long motorway type driving.
Mines been done twice in around 25k miles, it’s horrible what comes out if left for say 40k miles. For 1tr bottle about £14, not expensive.
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Would the same logic apply to the gearbox oil?
I’d expect the gearbox oil to take more punishment than the diff oil?
Yes. Manufacturers generally don’t include gearbox or different oil changes on service schedules - but anyone with any mechanical sympathy will know to change these fluids.
Gearbox oil choice seems to be quite critical on these cars. Any new oil is likely to be better than the old oil that is in there, but worth doing a bit of research and getting one of the ‘favoured’ types. Not sure what your box is, my six speed NC takes just over two litres in the gearbox. I have just bought some Ford spec Castrol Syntrans multivehicle for £14 a bottle from Amazon.
I am also changing the magnetic plugs. Last time I dropped the oil the magnets were past their best and not exactly effective, so that is why I am changing the oil again so soon, so that I can put new magnets in there.
I must admit I’m often puzzled re comments on how mucky the diff oil gets.
Mine was changed at 4 years/25.6k miles (dealer service, 2010), then again by me at 72k miles (about 4 years later). I’ve no idea what the dealer found, but when I did the 72k change in 2014 I was expecting smelly black goo to come out, based on comments from this forum, but what I got was clean oil that looked and smelt about the same as what I put in. Now on 107k miles so I guess I should do it again soon.
The only noticeable noise I’ve had so far from the back (apart from wind through the drains!) has been tyre noise from dodgy GSD3 tyres, and 2 days of pain from a stainless back box that I quickly swopped back to the original!.
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“I must admit I’m often puzzled re comments on how mucky the diff oil gets.”
d
Me too.
Only last year I dropped the diff oil on my '93 open diff Roadster. I thought…everything else is getting renewed…might as well…
Waste of time & money. The Hiroshima stuff ran out pretty much brownish honey coloured, not stinky and no swarfs. In went the new stuff anyhow.
However…I’d not ignore SWMBOs 2002 expensive LSD the same.
Changed that out twice over the last 15 years…but it drops out looking fresh as well.
Trying to figure out how a magnet can get “past its best” …
They forget how to be attractive, it’s inevitable with old age really…
In the old days magnets were supplied with ‘keepers’ to retain their magnetism.
One of the old jokes about cheap magnets was that if they were dropped the magnetism kept on travelling and left it when the magnet stopped on hitting the ground.
Modern magnets are better behaved, but can still lose it without any provocation.
Reminds me of my wife 
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As above. Cheaper magnets lose magnetism very quickly if heated, or more slowly if kept cool.
The ones on my 2008 NC were not strong enough to hold up thier own weight. I got new ones from MX5PARTS, but the diff one was just as bad as mine. I am guessing very old stock. The gearbox one I have not yet seen as it had to be ordered in from Mazda.
I bought a Gold Plug replacement for the diff; but the gearbox one is harder to get one that looks the same (very long with a protruding magnet) so am hoping the Mazda sourced one will be ‘fresh’.
So,
You are are still a handsome rake & legend in your shaving mirror 1st thing then? 