Best way to remove spinning bolt off bumper on FLD?

I got rear ended awhile back and am trying to replace this bumper. I removed all bolts, except 1. This one just keeps spinning and I can't get a wrench behind it due to the location. It appears it's a 3/4. I may try a longer wrench tomorrow, but want to pick your brains before I get started.

 

Small grinder with cutting disk.
Make several cuts each , time till you hit the washer..
Rinse and repeat till head off the bolt is smaller then the inside off the washer.

 

Possibly use a pry bar or long screwdriver to trap the nut, then zap it with a impact.

 

Die grinder to cut head off.

 

Use a high speed impact

 

I’ve used a big screwdriver more than once, jammed in against the nut. Be sure to use SS nuts bolts and washers, when reassembling. A flat washer between the bumper and bracket, also. To keep from dimpling they new bumper, when it’s tightened up.

 

The stainless is part of problem. Stainless on stainless bolt/nut almost always get galled togther especially when running them together with an impact wrench at high speed. You need a lubricant or antisieze when installing stainless hardware. If you can get away with it a standard zinc or nickel coated nut will work much better on stainless bolt for ease of removal the next time. Assembling by hand will also keep the heat to a minimum which is what can cause the threads to lock together.

 

That makes sense, a regular nut, I used all stainless on my steps. Once they’re tight, that’s it. Have to snap them to get off, first time I’d ever heard of SS galling together. And it happened immediately, I torqued them a lot, couldn’t get them off.

 

Great answers !