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G'Day,

Had a working bee on my NA6 today, and wanted to replace G/Box oil, tried for 45 mins to get the filler plug un-done. Anyone got any trick to loosen a seized filler plug.

TSM

Spray it with WD40 and let it soak overnight.
Don't stress if you can't get it out, you can fill it from the other side via the speedo sender. But don't fill it to overflowing as it's higher than the filler plug.

It's been a while, but isn't there another plug of some sort (hex head) on the filler side?

Try a couple of light taps on the end of the filler bolt, the idea is to dislodge/crack/break whatever is seizing the threads of the bolts. Similar to how a rattle gun works..

Worse case scenario, grind a very large bolt into the square shape you need, but slightly oversized. Tap it in with a hammer, tack weld it in place on opposite sides, use the appropriate sized socket on the bolt. Sucks but it works.

Dann

Take the car for a drive to warm up the box then try and remove the plug.
Be careful when draining the oil as it may be hot.

Thx all,
Will try a few things next weekend, if all fails will go with the speedo sender option.

Thanks again everyone.

TSM

u can always try tightening the bolt slightly to losen the thread
and im talking mm's of movement - any movement in any direction should help.

but as 1red5 said - wd40 works wonders! - but leave it soak for a few hrs at least!

heat often works but not sure if say a hair dryer might assist. The usual prob is not using the right tool or not having the right access and leverage. Having it on a hoist would help- a mechanic would do this for a nominal sum. It is probably a good plan to remove it as it will remain a prob the next time. I could not remove either of the plugs on the diff- I purchased new plugs - a mechanic removed the old plugs without comment- I simply could not get good access. .

I don't understand why car manufacturers have to use a square headed filler bolt instead of a good old hex bolt for the gearbox. At the best of time, even a large crescent wrench which is not the best tool but with good leverage would round that bolt if it's on too tight. If that bolt is too rounded from all your effort, I would sacrifice it and use a monkey wrench instead and get a new bolt. The filler bolt is self tapering so you don't need to gorilla fit it either. For the diff bolts, I suggest you leave them alone unless you have the correct 6-point sockets to fit. I had trouble removing my previous NA's filler bolt until I got a mechanic to loosen it for me.

^ Well, it's probably designed for ease of identification and to dissuade any oil changes unless you're certain of what you're doing.

A couple minutes of careful heating with the mapp gas torch and I was able to get mine free... tried to heat the gearbox casing more than the plug.

They use them for the same reason that fords have torx bolts on only the front 2 visible cam cover bolts, and regular allen for the rest of them. If you dont have the right tools you probably shouldnt be in there.

Dann

And, for what it's worth, a square is better than a hex for transferring torque - the geometry has a better balance of torque to contact stress. Ever wondered why socket handles have square drives instead of hex ones?