Adjusting Nut Front Park Brake Cable

[COPOZ/28]

Does anyone know the hex size and thickness of the pair of 5/16"-18 adjusting nuts (GM #9417954) on the front parking brake cable?

Are they the standard 1/2" hex for a 5/16"-18 nut or are they the oversize 9/16" hex?

They could also be thicker than a standard nut to permit an open end wrench to hold the one nut (the nut that is against the cable guide) while the 2nd (locking) nut is tightened.

Also, I've found conflicting info on whether these nuts are phos/oil coated or zinc plated.

Thanks for the help.

[169INDY]

AMK
5/16-18 GR5 FINISH HX NUT PHOS. 12 pk
Phosphate & Oil
B-12782

I think most here have found (*Origs) them to be a Std 5/16-18unc Hex Nut with no plating, pretty std item.

I agree it take a narrow comb or thin crescent to Jam them.