Just like to also say thank you to beinet1 for posting up this fantastic how to guide. over 11 years later and it's still coming in very useful.
Followed this guide to change the gearbox oil whilst replacing the 2/4 brake duty solenoid on my dad's 75 today.
Only thing that was odd when doing ours was, we drained the gearbox via the sump plug and that removed 3.5l of gearbox oil. I then added 4l of new fresh oil, and then removed 4l of old oil via the line from the oil cooler. We then added another 3.5l of new oil + around an extra 200ml to account for spillages. I then ran through each gear for 10 seconds each whilst stationary as instructed. All was done 100% as shown in the instructions in this OP.
However, when checking the oil level by removing the level plug firstly whilst the oil was cold, and then again once the oil was warm (the pipes between the gearbox and oil cooler were warm to touch) approx 2l of oil came out in total from the level plug.
We definitely got our measurements correct and definitely put in the amount we took out. I bought 2 5L cans of gearbox oil and still have 2.5L left in one can. The old oil has filled one of the 5l oil cans + 2 x 2l bottles (the extra 2l being what drained from the level plug). Car was on level ground on the driveway.
The only thing I can think of is maybe the gearbox oil had been changed in the past (we bought the car at around 85k miles) and had overfilled it at the time. It's now on 215k miles so don't know if having it overfilled for that long would cause any damage. Given the car a good test run (around 10 - 15miles) and all is running well.
Just hope it has the correct amount of oil in.
The car now drives super smooth after changing the gearbox oil. It's back to how smooth it used to be when we first bought the car, can't feel the gear changes at all
