Update
All the materials arrived for the service. Modified Sump pan & filter kit for the transmission, diff., transfer box and engine oil plus filters and front caliper service kit (Pistons, seals etc.). Overhauled the rear calipers when I did the rear suspension a few months ago and it made a big difference to the braking.
Now back to the original topic....
Had a read of the link relating to the transmission drain posted on the Disco 3 forum and today decided to make a start. Disconnected the top hose to the transmission cooler, extended it with a length of 10mm bore clear plastic hose into a bucket. The other half started the engine and I was astounded by the colour of the fluid which was being pumped out-it was jet black
!! Measured the quantity and there was 3.5 litres, not counting the 2 litres of clean fluid that I fed into the box via the stub pipe on the cooler. The colour improved slightly and I assume that the new oil was finding it's way back into the sump and mixing with the old oil that was lying there. The engine was run until there was no fluid going into the bucket. Next, I drained the sump and got a further 1 litre which makes a total of 4.5 litres that came out of the box in total...much less than I expected as the method is supposed to get most of the fluid out of the Torque convertor and gearbox interior. The capacity of the gearbox is given as 9.5 Litres from dry.
As I bought 10 litres of ATF AG55, i think there may be the possibility that I may need more if I flush through until I get clean fluid coming through so I have ordered a further 10 Litres.
Started to remove the screws securing the gearbox sump (Torx T40 heads). Used a TX40 socket on a normal ratchet and they came undone easily and was able to remove them with my fingers after the initial "Cracking". The one's along the sides are easily accessible but the front and rear are fiddly due to the restricted clearance-the Torx socket+ratchet would not fit in the gap. Luckily i have a set of "L" shaped Torx keys and it's manageable.
Decided not to remove the Crossmember or the rear gearbox mount.
Rain then stopped play, so it's back to it, hopefully tomorrow.
Tip for refitting the new sump pan and the engine under tray.......for the sump, cut a couple of pieces of M6 threaded bar about 2" long (Or cut the head off M6 Setpins) and get a couple of M6 nuts. Screw them into the tapped holes in the box about 4-5 turns around the centre of the sump or in diagonally opposite corners. Offer the sump up using them as guide pins and fit the nuts to just hold it in position to enable the proper bolts to be inserted then remove the studs.
I always use this method for fitting the steel under engine tray which uses M10 bolts to secure it. Makes life easier especially if you are doing the job single handed and lying on your back.Using a trolley jack to lift the tray over the studs is better still.