Filling d40 gearbox which plug

Hi guys, on the side of my d40 yd25 mt gearbox it has two plugs at different levels. the one on the side is 10mm hex same as drain plug. I assume this is the level for filling, i have checked the manual and the diagram showes it roughly in this location. But there is a bigger plug (approx 12mm hex and 50mm round) higher up right above the cross member facing down on an angle. does anyone know what is this plug for. As i dont want to over fill. There is a join near this, is the gearbox in 2 sections with the third the transfer??? I have searched the forum but to no avail... Any help appreciated...

The filler plug is the plug on the side, the one you remove to check the oil level (don't forget to discard and replace the gasket).

From what I can see in the manual (p21/72 of MT.pdf) the plug at the top has nothing to do with the oil level or refilling, it's called a "Check Shift Pin" - is that the one you're talking about?

Hey Old Tony, No mate , I had another look at the manual and it looks like the "return spring plug" page 27.... I was just checking it out because it looks as if somewone has tried to fill the gearbox through this one as there is an oil residue around the plug when i had my car returned from repairs.... I was worried it might be over filled. Will have to check it... Thanks for your help mate.....

Is there a problem is the box is slightly overfilled?

I have a car (Niva ) who's overdrive is known to suffer from oil staravtion problems. The remedy is to fill the box from the shift lever & deliberately overfill.

Yea your probably right. there wouldent be any oil flickers (no sure there real name) in a gear box and the breathers should releave any pressure on seals. I was surprised that the transfer case uses different oil (automatic fluid) compared to the gear box (75/85) might be something to do with the electric engager i suspect...

That return spring is not something I'd play with, it's also on p26 on the overdrive gear case.

I also agree with Joe - a gearbox shouldn't suffer too much from a slight overfill.