Mazda gearbox oil change

[Graham Hutton]

I've never changed any gearbox oil on any car I've owned and so would really appreciate any advice you all have for doing so on my 310R with the mazda 5 speed gearbox. I have a fully carpetted tunnel so would prefer to do it all from underneath if I can. Is it as simple as removing the plug on the side, sucking it out with a syringe and then squirting some clean stuff back in until it reaches the height of the plug? I guess the same would apply to the diff if I didn't want to remove the boot floor?

Any advice appreciated although I am sure many of you may be disgusted by my oversimplification here!!

[Graham Hutton]

Oh and also, any recommendations on gearbox oil and any oil based black magic for the diff that stops it making noise when manoeuvring at slow speed :-)

[KnifeySpoony]

No need to suck out - there's a drain plug on the bottom. Most of the noise you're hearing is the diff, not the trans, so fluid won't change anything there. One of the local spec miata gurus here in California who has rebuilt countless MX5 transmissions swears by Swepco 201 for syncro life, so that's what I'm using. It's a dino oil so needs more frequent changes presumably. I'm ok with that.

[Wrightpayne]

Top tip - make sure the filler plug can be undone before removing the drain plug!

[Rich Goddard]

Hi Graham

I found this useful from the MX5parts website (How to refresh the transmission on a Mk1/Mk2 MX5 - MX5 Parts Info), and the You Tube vid embedded within:

https://www.mx5parts.co.uk/information/how-to-refresh-the-transmission-on-a-mk1-mk2-mx5/

Rich

 

[Graham Hutton]

Thanks very much everyone! Easier than I thought. I've never really heard of people replacing the oil in the turret but clearly that is important too so I'll do the lot. The MX5 video is very helpful and I am going to use something like the swepco or redline oil because the Motul stuff is permananetly on back order it seems :-)

Really appreciate the advice everyone.

[MTW]

I recently changed my gearbox oil to Refline MTL, and the diff oil to Road and Race transmissions LS-90 diff oil which was formulated specifically to quiet down the noisey sintered plate diff, I have not driven the car yet to try it though! 
 

and as above, I did it all from under the car with gearbox, it's very easy. 

[Graham Hutton]

Thanks v much. BTW, I completely love the look of your car in mint green. If I build another, that'll be the colour for sure!

[MTW]

No worries! Ah thanks mate much appreciated!

[StevehS3]

I have read in several places (including RRT) that Redline MTL 75W 80 GL4 is recommended. Is this generally preferred over 75W 90 shown in the handbook?

[MTW]

I did email RRT confirming the statement on their site that recommended MTL for the Mazda gearbox. they actually responded saying they now recommend Redline MT-LV (a newer and lighter oil than MTL) I received the email after I had bought MTL, so that's what went in the box, but RRT's recommendation is now MT-LV, I might give it a try when I next change gearbox oil.

[7 wonders of the world]

The specsheet for the 201 oil shows it to be a GL5 spec which is not recommended for this gearbox, GL4 is, the former has additives to aid final drives the downside is this reduces friction between the syncro ring and the hub, slowing the change which encourages the driver to increase the pressure for faster shifts - result broken rings....

 

[ScottR400D]

A problem with a GL5 is that the EP additives are often sulphur/phosphorus based which can attack the metals used for synchro rings in a variety of ways and should only be used in a gearbox on the specific recommendation of the manufacturer. 
 

 

[KnifeySpoony]

According to Mazda - either GL4 or GL5 fluids are specified.

 

https://www.mazdausa.com/siteassets/pdf/owners-optimized/2000/mx5-miata/2000-mx-5-miata-owners-manual.pdf

[ScottR400D]

Should be OK then but I'd stick with GL4 as they also recommend that. 

[Geoff Brown]

As far as I know a GL5 spec oil is for axles so would not be best for gearboxes?

GL4 spec oil has generally always been the go to for gear boxes.

As noted below GL6 spec is now redundant but can still be purchased (Castrol B373 SAE 90 LSD GL6) but down graded to GL5. 

API Gear Oil Specifications

Spec	Status	Description
GL-1	Active	The designation API GL-1 denotes lubricants intended for manual transmissions operating under such mild conditions that straight petroleum or refined petroleum oil may be used satisfactorily. Oxidation and rust inhibitors, defoamers, and pour depressants may be added to improve the characteristics of these lubricants. Friction modifiers and extreme pressure additives shall not be used.
GL-2	Inactive	The designation API GL-2 denotes lubricants intended for automotive worm-gear axles operating under such conditions of load, temperature, and sliding velocities that lubricants satisfactory for API GL-1 service will not suffice.
GL-3	Inactive	The designation API GL-3 denotes lubricants intended for manual transmissions operating under moderate to severe conditions and spiral-bevel axles operating under mild to moderate conditions of speed and load. These service conditions require a lubricant having load-carrying capacities exceeding those satisfying API GL-1 service but below the requirements of lubricants satisfying API GL-4 service.
GL-4	Active	The designation API GL-4 denotes lubricants intended for axles with spiral bevel gears operating under moderate to severe conditions of speed and load or axles with hypoid (see note)gears operating under moderate speeds and loads. These oils may be used in selected manual transmission and transaxle applications where MT-1 lubricants are unsuitable. The manufacturer's specific lubricant quality recommendations should be followed.
GL-5	Active	The designation API GL-5 denotes lubricants intended for gears, particularly hypoid (see note) gears, in axles operating under various combinations of high-speed/shock load and low-speed/high-torque conditions.
GL-6	Inactive	The designation API GL-6 denotes lubricants intended for gears designed with a very high pinion offset. Such designs typically require protection from gear scoring in excess of that provided by API GL-5 gear oils.
MT-1	Active	The designation API MT-1 denotes lubricants intended for non-synchronized manual transmissions used in buses and heavy-duty trucks. Lubricants meeting the requirements of API MT-1 service provide protection against the combination of thermal degradation, component wear, and oil-seal deterioration, which is not provided by lubricants in current use meeting only the requirements of API GL-1, 4, or 5.

You can download API's Publication 1560 on gear oils for more detailed information.

[MTW]

I had a chance to test the car after using the Redline MTL and the results are fantastic, gearbox feels much slicker to use, lighter shift and no notchy changes whatsoever.

[Beagler]

Hi,

Will be changing the oil in mine with MX5 gearbox. I have seen the youtube vid further up where the guy removes the gear lever and sucks out the oil surrounding it in the turret and then replacing with clean oil as well as a normal gearbox oil change. Is this necessary. Car is 3yrs old and only done 12000mls so turret oil may be ok???