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Gearbox refill


New Member
Apr 17, 2016
Hi all,

I am having trouble filling the gearbox on my 80 series. According to the manuals it takes about 2.5L but having drained the box, I can now only get about 0.5 L in before it starts dribbling out.

Please can someone let me know if I am using the correct filling hole. Courtesy of this thread ( ) there are some nice pictures of the box.

Is the red circle the filler plug?
Yes it should be. When you drained it, how much came out?
Also, take care when tightening the nut - dont overtighten.

A previous owner/mechanic did that to my gearbox and its split at the boss, if I go to far the case opens up and leaks oil - new box waiting to be fitted - one day!
Best to use hex rather than multipoint sockets - 24mm IIRC, they can easily be rounded off. My boxes and diffs now have allen key plugs to avoid this and overtightening.
Possible build up of sludge in the bottom of the box? Affecting the level. Might be worth flushing a bit of clean oil through first.
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Just thoughts:

First there are gears just behind the fill plug, if your fill pipe is butted against them then oil will run back along the tube giving the impression the box is full.

Second, IIRC there is a narrow slot between the main casing and the rearmost section, takes awhile for oil to work it's way through to there, although I do think this is your problem.

Third mentioned above car should be level, not front up on ramps for example.

Fourth, also mentioned, how much came out?


Last edited:
Thanks for all the responses, really useful.

The driveway does slope slightly but only enough to stop the rain heading into the garage, a few degrees at most, and the rear of the car was pointing down so I could try with the rear of the car pointing up but I can't see that changing the possible quantity from 0.5 to 2.5L.

Unfortunately I can't say how much came out, I was doing all the diffs and transfer at the same time and used one drain pan, didn't even watch it as it was coming out. Lesson now learnt to try and empty the pan between fluid drops.

After the first time it appeared to be full, I gave it about 30 mins to settle down before trying again and the level was still flowing straight back out the filler hole.

My top guess from your responses would be sludge affecting it, I'm not sure how often it was changed by previous owners, if ever. At the moment I'm struggling to picture 2L of sludge but will give it another attempt at changing this week and measure how much comes out. At least my biggest concern of using the wrong hole to fill up has been set aside. Thank you.
I'd use a torch and a small mirror and have a look in there. Sludge is unlikely to be fair. Unless off roaded hard for a long time with water coming in through the breathers or a crack in the casing. Or unless the drain hole somehow blocked during emptying and it is in fact full of oil
If you have only put 0.5l in then you don't have much to loose by draining it again and this time seeing how much comes out.
It could be just getting airlocked. last time I did mine I loosened the plate that holds the shift lever in and filled it from there!
It could be just getting airlocked. last time I did mine I loosened the plate that holds the shift lever in and filled it from there!
If you fill it from the top, you need to be 100% sure its empty before filling. Othervise it will be overfilled.