When I get something really, really stuck on, I resort to the dremel method...
If it is a bolt or a screw, you dremel a new drive type (i.e. a good slot in the head), and work from there. For a nut, if you have enough access, you should actually be able to cut it off. I would recommend slotting it 90+% of the way through and then try to break with with a screwdriver or a chisel (may require multiple slots), so as to avoid damaging whatever is underneath. I have never used this method for removing a nut from any part of a car before... so use it at your own risk. I have slotted screws on a car before. They were those silly "security torx" type (with the nib in the middle to prevent regular torx bits from fitting), so I slotted them. Then I found out the next time I needed to remove a different set, that an o-ring pliers does a fine job of turning low-torque torx screws.
Obviously if you have to resort to dremel methods, you will need to replace the fastener (screw/bolt/nut/etc) you are removing with a new one. Of course, if it is rounded off, you'll want to replace it anyway.
have not tried blaster. What is it? this bolt plug is sitting in front of 2 quarts of oil, so I did not think a penetrating oil would help.
The torch method would be great, but this is the filler plug - the tranny case is aluminum and heating the plug would not do much. Possibly the surrounding case material? Thinking this though a bit.... aluminum expands at 3 times the rate that steel does, so heating the plug just might do it along with a vise grips, etc.
Its pretty rounded and can't get a socket to grab. Sears has those sockets with pins that will grab onto a rounded nut so I may try that along with heat.
BTW - I just finished a drive axle replacement and I used a impact wrench with a 32 mm socket for the axle nut. I could see problems with this nut so I tooled up for the job and it popped right off.
It's probably just under the head where it's sealed itself to the alloy, so penetrating fluid should do something there. A tip with this stuff is to drench it, than smack it from all sides with a hammer, then drench it and smack it again, then repeat, then leave it for 15 mins, not all that much longer, and not all that much shorter.
The reason for doing this is hitting it opens up microfissures around the interface of the bolt and the alloy, allowing the really thin penetrant to pump into them while you're hitting it. Leaving it for 15 mins ensures enough time for maximum freeing action by dissolving/converting oxides etc, while not giving long enough for the volatile components to evaporate away...
After that, getting a grip on it can be done by filing/grinding flats either side and using a pipe wrench, or slotting it and using a manual impact driver. Or, you can smack the burrs off it and pound an old and undersize socket on top of it, old because there's a 50/50 chance you'll split the socket.
AXLE NUTS sometimes there's no substitute for brute force on these the torque spec is 200 ft/lb on some fords, 160 ft/lb on some dodges, good luck shifting that with the 6 inch leverage of your socket wrench, you absolutely need, the right size socket, a real good one, a breaker bar and a cheater pipe if your breaker bar is less than about 3ft long. If bouncing up and down on the end of the cheater pipe doesn't work, put the car in gear, jack the car up on the end of the cheater pipe and if it hasn't broken loose by the time the tire is half inch off the ground, bounce on the car (carefully of course, don't want the jack going sideways and damaging stuff)
If you put the car up on stands, take the wheels off, half dissassemble the suspension THEN decide you want the axle nuts off.... heh, whoops... but that can be got around by bolting a big piece of angle iron across the wheel studs on one side, leaving room to get at the nut of course, and wedging the end of that up against the ground while you play strongman against it with a long cheater pipe, be real careful you don't push the car off the stands though.
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Oh I have daelt with axles nuts on Hondas to many times...I tried brute force and a nice breaker bar with a 32mm socket, then the impact gun...etc...this one is going to the final method, dremel with a cut off wheel...thinking I'll just spend the money on new axles anyways (Life Warranty ones times are like $60) since I have so many other new parts in the rebuild and the one cv joint feels a little stiff so probably needs replacing soon anyways, thanks for the advice guys, sorry to steal part of the thread...