Replacing part of the rear frame rail and torque box.

Welded up, inside and out

Back in August I removed the left rear torque box, and part of the frame rail.  Finally I have the inner frame rail, and the front frame rail complete, so it’s time to install the rear torque box, and the new frame rail section.

I ordered a complete convertible left rear frame section, since I needed the torque box, and a patch section for the frame.  It was cheaper to order the whole section then to order patch sections and the torque box.

Using the section of the old torque box, and frame rail as a template, I measured where to cut the new parts.  I made the new parts about 2″ longer to allow the frame rails to overlap to give me a stronger weld.  You can also see that I drilled 5-1/4″ holes for spot welds on both sides, and 4 more holes on the bottom of the frame rail.  I also ground one of the welds on the inner-frame-brace so that I can also overlap those. Finally a good coat of weld through primer, and it’s ready for fitting

First up I sanded the old frame down to bare metal and got rid of the undercoating and surface rust.  Next was test fitting the frame rail.  When I welded the passenger rear torque box, I had to clamp it back up against the inner frame rail, as it had sagged about an inch to an in and half.  Bearing this in  mind I lined up the new rear torque box and frame section on the old frame, and clamped them together (It turned out a good thing I had to cut away that part of the floor due to rust. ).  Then I clamped this assembly to the inner frame.  Using the frame alignment jig, and the datum line, I checked the position against the passenger side.  Once the torque box was in the correct position, I tack welded it in place.

Starting with the spot welds, and then seam welding the frame section inside and outside, finally I seam welded the inner-frame-brace.  Then I welded the torque box to the inner frame rail, finally tying the back of the car to the middle again.

With the torque box installed, I can patch the floor board. Since I had already did the same patch on the passenger side, this was an easy fix.  Taking the template I made for the passenger side and flipping it over to make it work for the driver side.  After a quick check to make sure it fit.  I placed the template on a sheet of 20 gauge steel.  and traced the outline.  I then cut it out, test fit, and trimmed as needed.  Then using a magic marker I traced the outside of the old floor and the frame rail on the steel.  Using the lines as a guide, I drilled 5/16 holes to allow me to spot weld the panel in place.  Once the all the prep work was complete, I primed the panel and welded it in place.

Next time I patch the cowl vents, and the cowl rust holes.