gear box oil change and additive?

I’ve got a slight crunch into second when cold so I’m going to havea  go at changing the gearbox oil so a couple of questions. What oil and how much should I use?, Can I add something like Slick, molyslip or Wynns additive to help with the crunch?, should I not bother 'cos they’re all like this?


2002, 1.8 sport. just under 30K miles





RedLine MT90 will help a lot with the crunch, don’t put additives in the gearbox

Capacity is around 2L

You can buy it from Opie Oils
oilmans website :
e-mail :
tel : 01209 215164

Thanks for the reply, the link is dead but I’ll have a look for the product


 I used Silkolene Sylktran SYN 5 75w-90. Get 3ltrs from Opie
Oils (15% discount at the mo’) and there’s enough to do the diff
aswell. Still a sleight crunch (mk1) in 2nd but new turret oil and
gaitors has helped a little.
Easiest way to fill the gearbox is a
length hose pipe with jubilee clip tightened to the bottle spout with a
piece of silicon tube (10mm I think) in the other end in the filler
hole (loop over the exhaust in a mk1). Let gravity and a squeeze work
but also pierce a hole in the bottom of the bottle to let air in. (Stps
a vacuum being created).
Go for a drive first to warm the oils up first. 
car up level on axle stands, undo filler nut (14mm square) first, then
the  24mm drain plug and hold your nose because it
stinks.[+o(]  Clean drain plug, new washer and refit, then fill er
up, nearly 2litres. Then do same with the diff. (23mm hex  filler,
24mm drain).
The nuts should really be torqued up, can get you the figures if you want.[8-|] 

link now live and I’ve found the oil. around 2 litres, so do I order 2 or 3 litres? sump washers? sizes please. getting the car in the air isn’t a problem but the location of the gearbox drain and fill might be. I’ve got a car lifter which lifts from the midpoint of the wheelbase. so anything underneath thats right in the centre is difficult to access. I can shift the car forwards or back about a foot either way before it becomes unstable so is the gearbox towards the front or rear of the car from underneath, I’m guessing the rear?

 torques figures would be good thanks


2 litres for the gearbox, one litre for the differential.  Aluminium crush washers for the gearbox drain, differential drain and differential filler plugs are the same part as for the Mk.1 car’s sump plug - Mazda part no. 9956-41-800.  Last time I bought a packet of 5 from Mazda it was about £3 IIRC.


Is that a perfect fit for the filler nut?

Ive been meaning to do this job for ages but havent got a spanner that fits, but if this is right, I know what to look for [:D]



what nice chaps they are. phoned them up, mentioned the above advice and got 10% off. ordered 3 bottles and got another 15% off!


fantastic, thanks all and especially opie oils



 You can use a 14mm open ended spanner or a 15 or 16mm (can’t remember which) double hex socket fits.

5/8th’s perfect fit

Will One of these do the job?



Why buy cheap junk from China when you can buy halfords pro range, for another £0.14?

Thank you, will get one tomorrow and give it another bash!!

 What is a double hex spanner as this is also mentioned in the teq faq section?



A 12-point socket or ring spanner, as opposed to a 6-point one.  You can use a 12-point one on a square plug.

This is the problem I have.  I bought the same stuff for my last MK1.  I used a length of tube with a funnel on the top passed up through the engine bay.  Good job I overbought as loads of it ended up all over the driveway.  Was going to get Castrol next time partly due to the fact the bottles come with flexible tubes already fitted.  Any other tips on getting it in as the way it’s going I have to factor in quite a bit of “wastage”!

I thought I was smart buying laboratory-style squeezy wash bottles and snipping the tip of the spout off, but the oil’s too thick to squeeze through their slim tube in anything more then a slow trickle. 

So now I just buy Comma oil which has a flexible spout in the lid.  There’s just room to hold the bottle upside down above the filler hole and squeeze the oil into the box at a more reasonable rate.

I do hate spilling gear oil, 'cos new or old it smells utterly rank.

A look round the FAQs is a real good idea…

All done and dusted, used one of these to refil…

great bit of kit and no spills. Not made much difference to the gear change though but that may be because it’s so cold at the minute, not got abouve 2 deg C for a week now.  BBrrrr.


thanks for the tips chaps

Whats the best method for refilling the diff when you change the oil - does it require one of those squirty pumps or is there another way?