Tried Liquid Wrench and tighten first, then added pipe wrench hit by big hammer while pushing on breaker bar, just stripped teeth off (cheap) pipe wrench. Thinking of heating nut w/ MAP gas torch.  Anyone fought a big nut and won?

Hmmm.. maybe try a long cheater? Large impact?

Check out Jpaydirt on YouTube D9h part 10. Great way to loosen a tight nut.

Watched the Jpaydirt video - spoiler alert, they used backhoe to push on wrench - and I found a 2-1/2" wrench on Ebay that looks strong enough to hit with sledge hammer or push on with backhoe. I thought the 1" drive socket and breaker bar would do the job, but the way it flexes makes me think I could break the tool before the nut comes loose.

Why are you removing that nut?

Removing nut to build a hitch for a log arch - copying design from photo of Hyster hitch that went with the D2N winch.

There were several different designs and different nuts for those hitches, I can help you with pictures and dimensions if you need it when the time comes. Those nuts are usually pretty snug, but will come off with a big impact wrench or a slugging wrench, just takes some persistence.

Claremontcat wrote:

I thought the 1" drive socket and breaker bar would do the job, but the way it flexes makes me think I could break the tool before the nut comes loose.
 

Unless the 1" handle is low quality you should not be able to break it. I have had a 6 foot piece of pipe on my tee handle and doesn't even look like breaking. For a nut that size you could also try using two hammers to persuade it a bit. Use one as a dolly and hit the opposite side of the nut. i have had nuts come loose just using that method.

Heat it with a acetylene torch and make it red orange. Hit it with one of those Milwaukee M18 3/4" impact guns. They are very impressive. That may be all you need without any heat.
I doubt you'll make it hot enough with a MAPP gas torch.

heat it with a proper heating tip and oxy-lpg(propane) ( much better for heating) let it cool and try again (mapp torches are for soldering plumbing). if you have a cutting torch get a piece half inch plate and cut out a slogging spanner as its made of steel plate it doesn't matter if you bend it where as big spanners get expensive fast.

a mix of kerosene and diesel works well but it takes time soak it heavily and let it work reapply as it soaks in.
that thread might be a bit burred over file it tapered a bit that might help ive chased burred threads with triangle files and a hacksaw blade.

ive done as phil suggested too it works surprisingly well some thing about actually getting a proper hit on the part, the second hammer sort of acts like a mirror and reflects the force dont ask me the physics ive just had it work. works well on tie-rod ends and ball joints