Gearbox Oil Condition & Filling Questions.

[Chief]

Yesterday I emptied out the 12 year old oil from my 1098 gearbox:

old_oil_2.JPG (201.66 KiB) Viewed 354 times

old_oil_1.jpg (77.93 KiB) Viewed 354 times

Not too bad looking colour wise, there were some silver swirls in the main oil which didn't show up on camera (the black lumps are driveway dirt and not from the oil) and the plug was quite full of silver glitter.

Is it normal for there to be some swirls in the oil?

Today since the weather forecast had changed from a day of rain to sun, I decided I should re-fill the gearbox.
Unfortunately I didn't have anything to decant in to, so I had to use the measuring mark on the side of the main oil bottle which (as it had been used for the engine as well) wasn't at a nice position.

So, is there anyway when looking in the filler plug to know when it's more or less up to the correct point?
Should it, for example, come up to the thread of the plug?
Can you over fill the gearbox?
If it's slightly under, will it be "okay"?

I'd say going by the bottle I put in around 1.2 - 1.3litres. I did try taking some photos to show the level of the oil but the flash didn't illuminate the oil so all I ended up taking was a photo of a dark abyss.

Thanks

[philthehill]

Swirls in the oil are common.
Metal grains in the drain plug are also common.
Just fill the gearbox until it overflows from the filler plug. Let any excess oil drain away and then re-fit the filler/level plug.

[Chief]

Thanks - I did wonder if I could do that but on the off chance that was considered over-filling I thought it prudent to ask

[myoldjalopy]

Swirls in the oil are common.
Metal grains in the drain plug are also common.
Just fill the gearbox until it overflows from the filler plug. Let any excess oil drain away and then re-fit the filler/level plug.

Or just measure out the correct amount and check that it is up to the level of the filler threads before fitting the plug again.

[Chief]

Well it's all filled up now, seemed quite thirsty for oil in fact (and no, I didn't have it pouring through the top and out the bottom ) have to ask, how tight should the top and bottom plugs actually be?

Reason I ask is, I know there are warnings about not over-tightening and damaging the gearbox casing, and I can understand the lower plug being fairly tight to stop all the oil pouring out onto the ground, but the top plug?

It was about the same tightness as the lower one (requiring two hands on the socket handle for enough leverage and more effort that I'd have thought necessary) and I just wondered if the top one really had to be that tight? (because it probably isn't quite so tight anymore, but I'd have thought tight enough).

[philthehill]

The filler plug has a taper thread so does not need to be excessively tightened. The plug needs to be just nipped up and an extra tweak of about 10 degrees should do it.

[Chief]

The plug needs to be just nipped up and an extra tweak of about 10 degrees should do it.

Thanks, that's probably about what I did judging by how it felt