Hi Mx5 OC. My model of MX-5 is: 2009 NC1 2.0 Sport, I’m based near New Forest (Wessex).
I’m having some problems with my gearbox, my car has covered 40,000 miles and I’m having problems with 3rd gear under medium/hard acceleration. It seems to pop out of gear and goes into neutral, which when trying to overtake or pick up speed is very embarrassing and painful to the ears, all the other gears are fine. The box is notchy as expected with the 6spd. Any ideas what before it goes to Mazda for a diagnosis? Thanks
I’ve come across a 6 speed NC jumping out of gear, can’t remember which gear it was, but one of the nuts had come loose on the end of on one the shafts.
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Hmm, how would one identify this possibility without crawling under the car or taking things apart?
Is there a simply identifiable mechanical symptom?
For example, how much free play would be normal on the gear lever when in a gear?
Engine off and cold, just now, my 25AE 6speed has about 5mm between front and back on each gear before I can feel it begin to think about moving out of the detent. I hope this is normal. 
With a mirror on a stick or a small camera like a bore scope camera. You shouldn’t need to take much at all apart the get to the linkage. You can always reach it, in my experience.
Your car will fall out of 3rd gear.
Basically none, but there will be a little bit of wiggle. It could still be pulled to neutral, possibly with a little grinding as the teeth let go if the car is running. What you are looking for here is play in the linkage, not specifically the lever.
Which is what I assumed my 5mm movement at the top of the lever showed as the usual default. There must be some slight freedom to let the gearbox detent hold the gear in the engaged position and ignore vibration, thermal movement etc
But if a nut was loose I would expect more, maybe. I don’t know, which is why I asked.
I’ve never bothered to study the linkage, and until recently strip-down manuals of the manual NC boxes were hard to find.
Oh, scratch that, anyway. I had a suzuki gearbox in my head, but actually the 5 doesn’t really have a linkage, does it? The shifter sits right on top of the box. You might find an inspection going in from the top fruitful?
You wouldn’t be able to identify it without removing and opening up the gearbox.
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Thanks Robbie.
That’s as I thought after having seen an exploded view of the gearbox.
This is why I asked my question about the normal amount of free play one might expect.
Why not check all the engine, gear box and differential mountings for ‘tightness’. Also check that the frame that goes between the diff and the gearbox is also securely in place at both ends. If all is well then it confirms that it is an internal gearbox issue.
There is adjustment on the side of the gearbox for 3/4th
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