Rear chassis construction: 1975 F100 spare parts truck

This section will be devoted to the back half of the pre-runner project. We are setting the rear suspension up with a single 3 inch shock on each wheel. Hopefully I will be able to swing bypass style, damn expensive though. I will be using 16 inch travel Fox racing shocks. Note the cage mounting brackets under the back of the cab. That is our CMB100 bracket with a BA200 bushing assembly. Ureathane cab mounts in the stock location are added. This gives us 8 mounting points for the cab now instead of 4.

We set up the rear end on a single leaf to mock up and cycle the rear suspension. A typical Autofab rear kit will have 18 inches of wheel travel. Notice the 2 link installed and cycling as well. This is a very important step to do. The 2 link kit controls the pinion angle, determines the rear end location under power and prevent the leaf springs from breaking. The pivot locations of the 2 link kit is extremely critical for proper rear end geometry. They have to be correct for the spring to work properly.

With a rear hoop located we fabricate an upper shock bracket assembly. It is necessary to plan your reservoir exit and mounting at the same time. Note we are not welding to our Ford frame. Everything is designed to bolt on. You will see reasons for that later. But it is nice to be able to take the whole unit off and do the welding without having to work around a frame and various other interference. We are using our BA200 bushing assemblies in the construction for a convenient bolt on method. Some folks like to solid mount the chassis. This is acceptable by making a plate that bolts onto the frame and then welding the cage tube to the plate. One of the reasons Ford trucks has a reputation for making strong trucks is their frames. They are made from alloy steels with tempering processes that increase strength. They are somewhat like a spring but not that hard. Ford would never weld to the frame except on the edges. I am talking about the frame rails themselves. No welding on the face of the frame. Another reason is the C design over the boxed and welded design. This is one reason why you do not want to weld onto Ford frames.  The other reason evolves from being a mechanic as well as a fabricator. Build the truck so you can work on it. Are you going to work on it the clean way with tools or use a cutting torch?   Nothing will last forever so you have to consider prep and maintenance work.

The next step was easy. Just throw some more tubes in the back along with the original shock hoops and the rear chassis is pretty much complete. LOL right after about 80 hours of work he he. Note the 3 mounting points to the frame on each side. There is an X brace in the middle that serves as a tire mount as well. The rear tire is mounted on is own structure and kind of hanging off the back of the frame. I surround the tire with a rear bumper. Yes I like 2 spare tires. I have been in the middle of Mexico before and had more than one flat! Note how the shackle and spring hangers all bolt on. All the rivets in the frame are removed and replaced with hardware I can torque down. Rivets loosen up after off road abuse.

Send E-mail to john@autofab.com with questions or comments about this web site.
Last modified: July 15, 2008