I should start with the warning that you can't rebuild a unibody to manufacturer
specs unless you have a terrific shop and skills. This rebuilt unibody would
certainly perform differently in an accident. Our new subframe member is
the longest piece we need to build, which runs from back of the driver side
floor pan up to the front-end crossmember. The first challenge for fabricating
the piece is getting the angles right at the joining surfaces. The floor
bumps down behind the driver seat, which is where the original subframe was
welded up. I plan to attach the new subframe with a bolt through the formed
structural member that runs across the passenger cabin right under the front
seats, so I need to cut that angle on the piece, or shorten it. The finished
end is shown to the right, I'll make up and leftover space between the edges
and the floor with Bondo.
The more challenging fabrication is where the subframe intersects an old
repair at the front of the car, just past the crossmember. The repair was
a large piece of angle iron, about 3" on side, which was welded into place
by a friend seven or eight years ago, when there was still a subframe to
weld to. I cut the angle into the piece at the left, and then bent the flap
over, as shown in one of the later videos. While welding the flap closed
would have helped solidify the piece, I decided against welding anything
for the time being, and later cut the flap off in an attempt to fit the piece
better to the old subframe. It's not really possible to build a new unibody
unless you start from scratch, I'm just trying to patch up the old one.
The picture to the right shows our new subframe member installed, though
not bolted up yet. You can see the crossmember (above the black jack) to
the right, the upper surface of which is about an inch higher than our new
subframe element. As I type this, I realized that if I'd turned the steel
tube on end, I could get that inch without having to do anything else, though
I might have to cut a slot in the side to accommodate the remaining subframe
over the stub frame. It would in the subframe running an inch lower when
it get back to the floor, which wouldn't be great. Another option would be
to cut a two inch wide slot in the end of our newly fabricated piece and
bold in a a few inches of the tube turned on its side. The videos below show
a few steps in the rebuilding process, nothing too fancy.
