Replacing Your Mopar Trunk Floor

A 3M Clean and Strip Disc works great to clean up the inside of the brace. This car will eventually be E-coated, but 3M Weld-Through Primer or a product such as POR-15 can be used to protect this inside surface.

The torched edge on the replacement floor from the junkyard needs to be trimmed with a cutoff wheel. Chris scrawled a guideline using a straightedge, being sure to use the business end of the Sharpie.

Chris replaced the floor and again traced around the outside so he could trim the edges of the original floor and leave a slight overlap. He reinstalled the replacement floor and tack-welded it in place so it stayed put while we made the final cuts.

Using a good cutoff wheel, Chris cut through both pieces in the center of the overlap, peeled back the excess, and placed a tack weld about every inch or so. He aligned the gap by prying up on the floor with a small screwdriver to be sure both parts were perfectly even before placing each weld. Since the new trunk will drop down into place, he made sure to keep the cutoff wheel vertical so the gap didn't get too large. In this case, it was especially important along the front edge where the panel slopes upward. This is why you'll want to get a panel that's cut all the way out to the trunk extensions. Remember where that center brace is located so you don't hack through it.

Once the replacement panel was tack-welded in place, Chris went around again and placed another tack weld between each of the first round of welds. To avoid any heat buildup, he quenched the area with compressed air and moved around.

When the second round was done, Chris did it again. At this point, the welds should all be about a quarter of an inch apart and ready for the gaps to be filled with a few quick tack welds. Don't run a short bead here-this is not stitch welding. Instead, tack-weld the tack welds together. While a trunk floor is not as sensitive to heat warping as a quarter-panel, the goal is still to keep body filler to an absolute minimum so the seam becomes invisible.

Chris ground off the excess bead with a 3M weld-grinding wheel leaving a very slight crown to avoid touching the original material. If you spot any pinholes along the way, go ahead and place another tack weld to fill them in.

Chris ground the area with a 3-inch 36-grit weld-grinding disc and an 80-grit disc on a DA to get the area ready for a skim coat of body filler.

The final job was to hold the floor tight to the brace and plug-weld the two together. Chris finished the welds just like the seams to make the car ready for filler and sealer.