MK3 NC 5 speed gearbox and diff oil change - socket sizes

Technical Area Engine, Transmission, Exhaust etc
2

I’m looking to change the gearbox and diff oil on my sister’s car (MK3 MX5 1.8 5 speed manual). I had it up on stands this morning just to have a look to see what socket sizes I’d need to get etc…

The diff doesn’t seem to be an issue, confident I’ve identified the filler and drain plugs and look like 23mm (fill port seems ever so slightly smaller) or 24mm.

 

However the gearbox ports… again looks like the drain port is 24mm but the fill port looks like a square socket that you’d plug into… Although it doesn’t seem to be 1/2" square drive size, so I’m wondering if anyone knows what type of socket this is so I know what attachment to get?

 

Thanks!

3

After a bit of research looks like it’s a 14mm open ended spanner, also sounds like it might be some fun to try and get it off :slight_smile:

4

Well I got my filler off fairly easily although access is a bit tight. The more difficult bit is getting the oil in. I used an old EP90 oil bottle I had which had a long spout on it to squirt the oil in but it took a few fills of the bottle and was quite a fiddle.

Ian

5

 

Remember to loosen the filler first before you drain the oil.

If you drain the oil and then have a problem loosening an over tight filler  ….

I used one of these to refill the oil

https://www.amazon.co.uk/Sealey-AK46-Suction-Syringe-500ml/dp/B000RA0XLO/ref=sr_1_8?ie=UTF8&qid=1534505766&sr=8-8&keywords=oil+syringe

 

Richard.

6

Some great advice here http://revlimiter.net/blog/2017/02/nc-mx-5-miata-2006-2015-oil-trans-diff-fluid-change/

7

Cheers guys, yeah I’ve changed the gearbox oil on my S40 so already know the wise advise of checking you can undo the filler port first haha!

The oil syringe also sounds like the way to go, thanks for the advice! :slight_smile:

8

 

You could be surprised how easily it will released, they don’t torque them up too tightly. A tip, wrap some PTFE tape around the thread when replacing the plug.
The 6 speed has a similar fill plug to the drain plug, new washers required when replacing.

9

Will try that thanks, and really?

I’d read of people have real trouble getting the filler plug undone.

 

10

Hi rather than start a new thread do you need to replace the washers seen some say yes others not bothered

11

Absolutely YES.

Dealer replaced my diff oil, but re-used the filler washer, most of the oil leaked out again over the next few hundred miles until they got some more crush washers in stock, the pong from where it was dripping on to the exhaust was awful.

12

 

We sell sump plugs with 18m copper washers at work cheaper than I can buy crush washers looking on Google guess a sump washer is the same thing.

13

I put in new washers too, were only a couple of quid off Fleabay and I got about 10… :slight_smile:

14

https://www.ebay.co.uk/itm/M3-to-M24-Metric-Solid-Aluminium-Sealing-Oil-Sump-Plug-Crush-Washer-Banjo-Garage/281903432810?hash=item41a2c1046a:m:mkK8dl6wPhz3ulbSDj4MVwg:rk:9:pf:0

 

Guess these will do, do I need M18X23X1.2 sell car components at work all day happily, but hate little bits and bobs. 

15

90% of the time the 14mm square filling plug for the 5 speed box that is used from the Mk1 / NA throught the Mk3 / NC comes off without any problem but sometimes it is very tight. I would also advise as stated above that you have some PTFE tape in the toolbox, available from the local DIY store to wrap round the threads prior to replacing the plug.

I made up this handy spanner made up from a 17mm ring but if you have a MK1 then you may want to use a 19mm ring one end and a 14mm open ender at the other end that helps if the filler plug is tight.



As always a MigWelder is a handy tool or a TIG if you have one.



Wayne at MazdaMenders has gone one further closing off the open end of the 14mm.

http://www.mazdamenders.net/forum/viewtopic.php?f=91&t=3050