N_Jay

It is Hex, and you need to get a good fit because filler plugs with their wide shoulders are always hard to open. (not to mention mechanics who love to over tighten them)
Get a solid fit and use a LONG breaker bar, and a hammer to add a little impact force.

You can try heating the area gently and then using a penetrating oil spray to cool the plug.

You don't want to get it to the temp that cooks oil, but heading towards boiling is OK.

tester123

I got that plug open by using a Hex bit of correct size with (don't remember 8 or 9mm) a tight fitting wrench (closed side). Slide the hex key through wrench and into the filler plug. Hold it from moving and use a pry bar to push the wrench (counter clockwise). Do it carefully and it will come out so easily. Tighten the same way.

As I mentioned, pump out the oil to a clear container and compare with new and you'll see the difference. My car runs much better after all diff fluids have been changed.

N_Jay

You don't need to tighten it the same way (that is how it gets over tightened).
If you want put a very little anti-seize on the mating surface of the plug head, you can put some on the threads, but keep it at the head end and away from where it will get into the diff.
Then tighten normal arm tight (Don't have the book for the Ft-LBs with me), but just a good tug with an 8 to 10 inch wrench is plenty.

tester123

Over tightened or not, I don't plan to change the fluid again. It's done at 100k and IF the car makes it to 200k, plan to keep driving like that until it buries itself into ground. Only regular maintenance and minor repairs from here on.

N_Jay

Yes, but instructions like yours (when when executed at under 100K) make servicing a pain for all of use working at something over 100K.

rocketman4321

For future reference, the fill plug is an 8 mm hex. If the drain plug's a hex, it's a 6 mm. In my case, the drain plug isn't hex any more--sigh.

tester123

I don't know about you but, I think people on this forum (who are mechanically inclined) know what they are doing and just look for clues to help expedite the repair. I am pretty sure they'd know how to tighten a filler plug, "N_Jay".

What's your car year/model/mileage?

N_Jay

I assume that people reading these thread are of all different skill and experience levels, and that is why good information is important and incorrect info needs to be corrected.

Which car?
The A6 is an 00 with 130K, the parts A6 is an 02 with 132K, the Touareg (V8) is an 04 with 123K, the E350 is an 07 with 118K, the GL320 is an 08 with 120K, and the 914 is a 73 with a broken odometer.