Fatman Chassis Build - Fast Frame

This is the rear section of the framerail being slipped into place over the twin tabs in the main framerail.

Note that both sections of the frame have been ground to a bevel. This gives the weld ample penetrating surface and ensures the wall thickness is not compromised after final grinding.

With all the pieces in the jig, cross measurements are taken to ensure everything is in the correct position. It pays to double-check even when you are using a frame jig.

After the side rails have been welded, the front crossmember is located by the frame jig. Once again, all measurements are double-checked prior to welding.

With the front crossmember tacked in place, our perimeter frame is looking like a full chassis. The tubes extending from the crossmember mount the lower control arms.

Since the rear suspension will be coilover shocks, a simple box tubing rear crossmember is installed.

The center crossmember incorporates a driveshaft loop and extends past the framerail to accommodate the outboard four-bar brackets. Note the perfect fit of all brackets. The chassis is upside down to ease fabrication on the rotisserie.

Satisfied that the crossmember is properly located on the frame, the four-bar brackets are welded in place.

The Fatman Fabrications crew tack welded the four-bar brackets to the 9-inch Ford housing and now it is time to locate the rear in the frame.

The rear axle housing brackets are two-piece brackets that circle the entire axle tube.

The axle housing is located by installing the four-bars. At this time it is imperative to locate the exact axle centerline. Pinion angle can be dialed in by adjusting the bars.

The four-bars are in place and the end plate has been tacked in the crossmember. Note the neat and strong box tubing gusset from the framerail to the crossmember.

The brackets for the diagonal bar mount to the four-bar bracket. This bar centers the rear housing and a piece of tubing is cut and welded to the bung in the photo.

Josh Layton measures from the axle flange to the outside of the framerail to ensure the axle housing is properly centered.

The bar has been cut and tack welded to center the housing, all the brackets are tack welded in place before any final welding is done.

Now that the rear axle housing has been precisely positioned, the upper shock absorber mount can be located and tack-welded to the framerail. A bar simulates the shock absorber.

After double checking all locations, Chris Elliot takes the housing back on the bench and TIG welds all the brackets to the housing.

The final piece of the rear suspension puzzle is locating the sway bars. Coilover shocks and adjustable sway bars should make the truck handle like it’s on rails.

Here we see the finished four-bar bracket welded and ground to a final finish. The chassis is as good looking as it is strong.

Looking from the rear, the sway bar hugs the shape of the rear axle perfectly. This makes for a clean appearance while working wonders for handling.

All the cab and bed bolt holes are drilled into the frame with an access hole on the inside framerail.