This just happened to me on one of my vehicles. Had to tack weld the stud in place with the mig. This is common as the nut becomes rusted on and when torque is applied they break loose. Got to remove the seats, pull the carpet and weld. Should you not want to pull the carpet, you might get by by placing a sheet of sheet metal round the stud with a 1" hole as a carpet protector.
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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE " [This message has been edited by Dennis LaGrua (edited 08-04-2019).]