Filling the gearbox will fill the overdrive. Draining the gearbox will get most of the oil out of the overdrive.
If it is J type you have to remove the sump and, ideally the filters and give them a good clean. Unfortunately you will need a special tool to remove the filters - though you might be able to make one.
Hi, Well on the 'D' type that I have the plug on the o'drive unit is actually marked 'Drain' & is at base of casing on back of g'box. Not sure if it as clear on 'J' type? If box/o'drive has lots of oily dirt then it might not be as easy to see. Need pic really. If I'm out in garage later will see what I can do. Cheers. G.
Just wondering if anyone can help me locate the oil drain and filler plug specifically for the overdrive on the gearbox? I have drained the gearbox but my manual says there is a seperate drain for the overdrive.