Mark 3-5 first gear clunk when cold. Oil reccs please

  1. My model of MX-5 is: Mark 3.5 Sport Tech
  2. I’m based near: Birmingham
  3. I’m looking for technical help or recommendations on: Gearbox oil & Diff oil (LSD)

There is a clunk when engaging first gear when the engine is cold.
This is not a big deal. I understand this is very common on mark 3’s.
But I’d like to minimise this clunk.

I’ve had my car for almost a year and a service is now due. I will
have the gearbox oil and rear Diff (LSD) oil changed at this time.
I don’t know which of these can affect the clunk.

Please can I have recommendations.
I hear that Redline is pricy but good. Namely:

  • Diff oil Redline75W90 GL-5
  • Gear oil Redline MT 90 75W90 GL-4

But the thing is that the Redline Gear oil comes in 950ml packs
and the capacity of the gearbox (from dry) is 2100ml.
Would two bottles totalling 1900ml (minus what gets stuck on
the inside of the bottle) suffice? Or would I need three bottles?

Or are there other alternatives?
Also as per Mick’s suggestion below, I’m now also looking for
Clutch fluid recommendations too.

Buy 3 x1 litre is the only way, though I put Castrol in mine.
Try having your clutch fluid changed as well.:+1:

I’ll ad that to my list above.

Dot 4 brake fluid, clutch shares the same reservoir so brake and clutch systems fluid change whilst you’re there👍

OK cool.
I already had brake fluid change on the list. :slightly_smiling_face:

Try adjusting Clutch pedal for minimal play BUT… MUST Have a little play! Test for minimal play hot and cold.

Also bleed the Clutch.

Did this NC 3.5 and it is now smooth… way better!



i used the DuratecNC oil and it made a huge difference to the 1-2 cold gear shift.


There is only one oil which works with a 100% success rate, any others are open to debate.

Is this Gearbox oil or Diff oil?

Hey there. I guess the above questions are for you too.
Where / how do I buy the DuratecNC oil?

Gearbox oil - google DuratecNC. But i guess the guy above is the same person!

1 Like

PM me or use the contact box on the site

It’s a bit slow at the moment as i’m moving house and workshop, but if you have some patience i’ll help you out. Just bear with me, it is worth waiting for I guarantee it.

Ford/Motorcraft XT-M5-QS is good stuff if you can get hold of it.

OK. PM on here sent.

My MOT & service is on Tues 5th Oct.
Would you be able to supply me by Mon 4th Oct?

Yes I can get some out on Monday, sorry for lack of replies! PM me your name and address and we’ll sort out payment later.

Cool. Paypal payment sent.
I look forward to receiving the oil. :slightly_smiling_face:

A few boxes going out today and tomorrow, tracking will be emailed to you.
Thanks for your patience. It will continue to be difficult for the next few weeks, but i’ll do my best to keep supplies flowing :smiley:

That’s brill! Thank you for your help. :slightly_smiling_face: