When I'm in a position where the wheel spins due to the tire being flat or nothing to hold it, what I'll do to crack the nuts is I will use my 18 inch flex bar with a deep 6 point socket.
I get positioned so I have a good grip point, then rotate the wheel quickly clockwise with the bar and socket, then very quickly reverse direction, turning the bar counter clockwise with as much force as I can. Usually the momentum of the wheel is enough to crack the nut loose. Sometimes have to do it a couple times.
I've done the same thing with a star wrench too. Or using a star wrench, I'll hold it with one hand and give the other end a firm kick with my foot.
2007 GMC 3500 dually ext. cab 4X4 LBZ Dmax/Allison - 2007 Pacific Coachworks Tango 306RLSS
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