Replacing the gearbox oil
As the car has just passed the 98,000 mile mark and Opie Oils were having a spend £30 and get free delivery offer, I though I'd replace the gearbox oil. I took the car out for a spin before starting to make the sure the oil was warm to assist draining. Don't start work straight away though as you may burn yourself.
[A] Start by jacking the car up and putting axle stands under the correct points. If you lie on your back and shuffle under the bumper on the passenger side of the car, you will see the drain plug. As I found out later, I have no idea what tool you're supposed to use to undo it...
[B] If you look at the front of the gear box just above the main radiator coolant pipe, you will see the plastic filling plug. The torque value for this is so low you'll probably be able to undo it without tools, always a good thing.
[C] Having found out that the square hole in the drain plug was way smaller than 3/8" and way bigger than 1/4", I was a bit stumped. I then figured that a bit of ghetto fixing would sort the problem. 10 minutes with my awesome new Metabo anglegrinder on a 1/2" to 3/8" adapter created the perfect tool!
[D] Having checked that you can undo the filler plug first, place a receptacle under the drain plug and remove it, it shouldn't be too tight. Lower the car to the ground and leave it to drain for 20-30 minutes to make sure the oil drains out completely.
[E] Jack the car up again on the axle stands before you continue. Remove the old crush washer and replace it with a new one (mine cost 78p from Westway Nissan in Manchester, surely the cheapest Nissan part ever!) Refit the drainage plug, the torque value is 16 ft/lbs.
[F] Now that the drain plug is fitted, you need to make a refilling device. I used a length of aquarium tubing (o/d 12mm) roughly a yard long and a plastic funnel. The tube was a push fit into the funnel so I sealed it up using some self amalgamating tape I must have bought when I fitted a Sky dish a few years ago. Run the tube down to the fill hole, there's a perfect gap to the right of the coolant expansion tank in front of the fuse box.
[G] At the other end of the tube, remove the fill plug and place the end of the tube into the fill hole on the gear box. If you wiggle it around a bit, you should be able to get about 3" of the tube into the hole so it doesn't fall out again. Stop sniggering at the back....
[H] You can now start filling the gearbox with the new oil. Pour a couple of glugs of the new oil in the funnel and quickly get under the car and check there are no leaks and that the oil's going into the gearbox successfully. The box takes 2.6 litres of oil so I put in two whole bottles and enough of the third bottle that the scale on the side said 400ml afterwards.

Once you're finishing adding the new oil, remove the tubing from the hole and refit the plastic fill plug. Make sure the black rubber washer is present, mine was stuck to the gearbox and I didn't even notice it until I was refitting the fill plug.
[I] If all went well, you should now have a gearbox filled with lovely clean oil . The 160SR takes 2.6 litres of 75w80 weight oil. I used Motul 'Motylgear' because it was what Opie Oils had in stock when I placed the order but any reputable brand should be ok.