Technical Tech week; " Flatten" an early Ford rear crossmember.

I am building a '40 Ford PU, using transverse springs front and rear and decided that this was my best option to lower the rear.

I started by leveling and locking the frame down on my chassis fixture. I next welded a stub of 1/2" square tube vertically in the spring center bolt hole, to maintain the location of that important dimension, and marked the height of the center of the crossmember. I also bolted an angle across the rear axle bumper holes to control the spread on the rear rails.

To make things easy, I formed up a sheet metal channel to serve as a saw guide. The next step was to layout the slits on each side of the crossmember.

 

Step 2,

I cut the center out and made the side slits.
I welded a plate to the center alignment stub 2. 3/4" higher than stock, and placed the
center section on and clamped it in place.
The next thing was to heat and bend the sides up to match the height of the center.
My thinking was bending the sides up before removing those sections would make a better appearing joint after welding.
Next thing was to cut and remove the side sections and trim them to reinstall at the new angle.

 

Step 3

With all of the pieces fit and tacked back together, I used some of the small trimmings to fill the gaps.
When finished, it will be tig welded totally inside and out, and fully ground smooth on the outside.

 

Rad.

 

I never thought about bending it first, then cutting, thanks for the tech....great work.

 

Marty flattened the rear cross member on my deuce roadster a few years back with the same amazing results. Thanks Marty!

 

Thanks for reminding me Jeff, on yours I didn't remove and fit the side sections, as it only required some massage for them to match the center piece. As I remember, it ended up moving the center bolt dimension 1/4" or so to the rear, and helped center the tire and wheel in the fender opening. Here are some pics of that one.

 

Nice work on both of those and it shows how to do it right. It also gives a definitive explanation of a "flattened rear crossmember" for a lot of guys who read that on the description of a rod or Fatfender Ford custom and go ????????

 

Very timely and great work on both rear cross members. I have used the flattened 40 in a Deuce also. I had to shorten it but it worked great. I was not as clean with my modifications so now I know how to do it right. I have a thread on here about raising the front crossmember have you done any of those?
Thanks,Lynn

 

Thanks guys for the kind comments and your interest. Here are a few shots showing the 3 1/2" clearance between the bed floor and the center of the crossmember. I think I want it to ride about 1" lower in the rear, it is only blocked up at present. I set it up to use a 42-48 passenger car rear spring, as they are 1 1/2" shorter than a 40, giving me 3/4" more shackle clearance at the sidewall using 8" wheels.

Lynn, I haven't done any modifications to the fronts.