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1. Remove the rear suspension and fuel system as outlined in a repair manual
2. Place the reinforcements in the correct location (bend rear plates at dotted lines to fit). Use a paint pen to outline the 4 steel reinforcement plates. Remove all the paint and undercoating 1” outside of the outline.
3. Use the two 12x1.5 bolts to hold each set of plates in place using the stock mounting hole.
4. The front plates have one extra 1/2“ hole and the rear two plates have two 1/2” holes. These holes are for making a rosette weld. Use a 1⁄2” drill bit to cut through the outer sheet metal layer. Do not drill all the way through! You only need to drill through one layer to help tie everything together once it is welded.
5. Fill in the holes with a rosette weld before welding the “dotted lines” and around the outer edge of the reinforcements. The front reinforcements do not need to be welded all the way around the plate, stitch welds are sufficient.
6. After welding grind down the rosette welds and any other high spots flat so theyre flush with the plates. 7. Clean all welding residue and use seam sealer on all stitch welds. Primer and paint all bare metal.
1. Place the two 3”x3.5” sheet metal plates in the trunk as seen below and using a paint pen, outline them. Now remove all the paint and undercoating 1” past the outline. Replace the plates, and use the paint pen to trace around them one more time.
2. Draw another line about 1⁄4” inside. Use a cut-off wheel to cut the sheet metal out following the inner line.
3. There are 3 rosette welds inside of each cut out. Clean the inner sheet metal BEFORE cutting. Cut out an upside down T section of the sheet metal between the three welds. The three spot welds are where the cracks begin. Use a cut off wheel, it helps if you have a used/worn down cut off blade.
4. Weld the upper sheet metal to the lower sheet metal around the area you just cut out. Weld all existing cracks in the sheet metal.
5. Clean all welding residue and use seam sealer on all stitch welds. Primer and paint all bare metal.
6. Place the 3” x 3.5” steel plates over the hole. Butt the plate up against the lip in the sheet metal toward the front of the car. Tack weld it in place. Place two more tack welds about half way down the plate just before factory sheet metal starts to curve down. Bend the rest of the plate to contour the factory sheet metal and spot weld in place.
7. Clean all welding residue and use seam sealer on all stitch welds. Primer and paint all bare metal.
8. Install the rear suspension in the opposite order that you removed it with one exception. When installing the aluminum cross member on 3 series or the steel cross member on M3 you will need to use the two steel spacers we provided. (pictured below) Warning: if you do not use the spacers you may crack the cross member. Place a small dab of RTV silicone between the cross member and the spacer. This will help keep the spacers from getting lost if the cross member is removed in the future.