Gearbox oil question/predicament

What is the recommended kilometres or time interval for when the manual gearbox oil should be changed and topped up. The original owners and Haynes manuals don’t seem to mention it, or have I missed seeing it ?

The Haynes manual shows me where the transmission drain plug is. Easy enough. It shows me how to remove the speedo drive to measure the oil and top up when the engine is out of the car. Great , easy enough when the engine is out of the car– how about for when it is still in the car you knobs ? Should I be trying to remove the speedo drive from underneath the car or from on top ? It seems to be a really awkward place to get access to.

The Haynes manual then tells me that I have to measure how much oil is from the top of the speedo mechanism once the drive is removed. And then it provides me the number of mm’s from the top to the oil level. Great.

Is it me or is this whole procedure an extreme pain in the arse ?

Given that the car has 225,000 klms on it and I don’t know when the oil was last changed (if ever), should I just drain all the oil out, remove the speedo drive and keep pouring oil in until it overflows before replacing the speedo mechanism ? What damage (if any) can occur if I overfill it/do it this way ?

2 plugs... One on the bottom is drain and one on the side facing the front of the car is filler.... I use a half inch ratchet to loosen them!!! Hope that helps... Just fill from the side till it starts to trickle out....

the speedo drive fill is for the pre 98 1.0 RS5F41 g/box,s, that have no level plug, but is an option on the other k11,s. (its a bigger orifice :) )
and you fill it level with the plastic cog down the hole iirc

What are the thoughts on this oil ? Anyone used it ? good/bad/indifferent ? i bought it because it was the only one that had a GL4 specification (as recommended in the owners manual).The rest were all GL5 oils.

And thoughts on using oil additives for the gearbox ?

http://www.supercheapauto.com.au/online-store/products/Nulon-Smooth-Shift-Gear-Differential-Oil-80W-4-Litre.aspx?pid=164767&utm_source=getprice&utm_medium=cpc#Description

mine,s mainly 10/40 engineoil lol, but i have 2 spare 41,s and dont really care.
some members say it goes a bit notchy with fresh ep75 (or whatever it is)

I use 80-90 gear oil, I'm pretty sure

i used Castrol Manual EP80W/90 before no probs.

to fill i simply remove the airbox, unscrew the speedo cable off, unbolt the speedo and pull the speedo unit out, then pour the oil down a big hose pipe & funnel

u fill the gearbox up till the level is 38mm from the bottom of the speedo hole and i recently discovered that the max level on the engine dipstick is also 38mm so use that.

Not sure what the speedo drive hole looks like but on the aussie delivered micras they have two plugs. The bottom large plug to drain it and a smaller plug towards the top you use to fill it up. Be warned though the plugs are Tapered plugs and are a absolute bitch to get out and you might find yourself doing a bit of swearing while getting them out :) Also I would avoid Castrol oils as my gearbox became notchy after using it and I keep meaning to change it to something better.

the speedo cable goes down into the back of the gearbox