With the body off being repaired, it was time to turn our attention to the chassis of Project Speed Bump and figure out just exactly the direction we wanted to go with it. In the interest of simplicity, it was decided that we’d be keeping the rear leaf suspension for now. However, we were going to notch the frame and give ourselves some flexibility for upgrading in the future, while ensuring we had enough rear suspension travel to match our Crown Vic setup in the front.
After a call to LMC Truck, we settled on the company’s simple 4-inch hanger and shackle drop to bring down the rear. Because the Crown Vic conversion lowers the front of the truck approximately 5-inches, its possible that the rear could still be too high, even with a 4-inch drop and a rear-mounted fuel tank. Because of these variables, we plan to dial in our rear ride height with a set of custom leaves from Deaver Springs once we get the truck closer to completion. In order to control axle wrap, we’ll most likely add some traction bars down the line, but at least the following mods get us closer to our goal of getting back on the road.
As with most 50-year-old vehicles, our truck lived a fairly hard life, and the frame was showing its age with various wrinkles and droops. To get the frame square again, the team at LGE-CTS Motorsports in San Dimas, California, put it on the table and massaged it back to its original dimensions. We then headed, frame in hand, back to Off Road Evolution in Fullerton, California, where the trusted fabrication skills of Mel Wade and crew were again put to good use.
Looking for a simple solution to notch the Ford frame, the guys at Off Road Evolution modified some dimensionally close EVO Manufacturing notch brackets usually reserved for modified Jeep Wrangler JKs with bigger axles and extreme travel. While notching the frame with the LMC rear shackle and bracket flip kit kit isn’t necessary, we wanted to insure we could go lower in the rear if needed and still maintain our ride quality. It also allowed us to mount a bumpstop inside the notch and not take up any of the valuable uptravel. While the welder was out, we took the opportunity to fill some errant frame holes from previous drivetrain swaps, repaired some additional frame cracks, and welded in new body mount Frame Savers from Jeff’s Bronco Graveyard.
In Part 4 of our build-up, you may remember we had a Dynatrac 60 rear axle built for us by Dynatrac in Huntington Beach, California, to replace our factory Ford 9-inch. With a minimum of 514lb-ft of torque from our Banks 630T turbo diesel engine, it was important to have a strong enough axle to withstand the twist and still allow us some room to safely increase power output if we decide to twin-turbo the truck later. With a manly 3.5-inch-diameter axle tube on the Dynatrac 60, our next challenge was going to be figuring out how to hang it from a truck with 1.75-inch-wide springs and leaf spring plates designed for an axle with a 3-inch-diameter tube.
As it turns out, in the off-roading world, it is fairly common for early Bronco (’66-’77) guys to dump the factory 9-inch axles for stronger aftermarket Dana 60s when running big tires and high horsepower. Enter fabrication parts company RuffStuff Specialties of Loomis, California, that just so happens to make U-bolt plates designed for the early Broncos, which mixes the 3.5-inch axle tube spacing we needed with a 2.25-inch leaf spring. It was exactly what we were looking for, proving that sometimes it pays to know what the off-road guys are up to.
With the frame welded, and the rear axle hung, it was time to strip the frame all the way down in order to have it blasted and powdercoated. What we ended up with was a beautiful new backbone to Project Speed Bump, and we left the fabrication portion of the build and excitedly looked forward to paint and body and eventual reassembly.
1. Our frame was in pretty rough shape, with cracks and corrosion taking a toll on the body mounts. You can see here just how thin and pitted our body mounts had become, making it a wonder how they were able to even support the weight of the cab.
2. Fortunately, the F-100 shares a lot of parts with the Bronco of the same era and Jeff’s Bronco Graveyard makes weld-in replacement pucks called Frame Savers for the body mounts. It’s a great way to repair the frame without having to recreate the original mounts.
3. There is not much to the factory spring hanger, but installing a new bracket and raising the effective mounting point of the leaf spring lowers the vehicle. It’s not uncommon for guys to just flip the factory bracket, but we wanted a beefier solution.
4. The rear of the leaf spring mounts to this factory shackle, and by replacing it with a longer shackle, we achieve a lower ride height. When you combine the new hanger with the 2-inch-longer LMC Truck shackle, the overall drop is around 4 inches.
5. Next, we removed the factory rear axle from the frame, giving us room to work on the leaf spring hangers and frame notch.
6. We then used a torch to cut the heads off the rivets holding the leaf spring hangers on.
7. Here, you can see the new spring hanger next to the old one. The LMC Truck hanger gives you two options for the leaf spring to mount, depending on how low you want to go. Both positions will lower the truck from stock.
8. The LMC Truck hangers are bolt-on parts. However, we decided to go the extra step after bolting them on and welded them to the frame for increased strength.
9. EVO Manufacturing is known for Jeep Wrangler and fab parts, but because the Wrangler JK frame and F-100 frame are close enough dimensionally, we decided to use some modified EVO Manufacturing JK Notch brackets as the basis for our F-100 notch.
10. With the location of our notch marked, we took out the cutting wheel and went to work.
11. After making a few test fits, and modifying the EVO notch brackets to work with our F-100 frame, we welded the pieces together.
12. We also welded a nut to the backside of the notch brackets, allowing us to easily screw in our bumpstop of choice when we get to the point of setting ride height and travel down the line.
13. Once the brackets were finished on the bench, they were placed on the frame and welded in place.
14. After completing the notch, it was time to hang the rear Dynatrac axle. Using spring perches and U-bolt plates from RuffStuff Specialties, as well as U-Bolts from Deaver Spring, we had all the pieces we needed.
15. The factory leaf springs were then hung from the new LMC Truck leaf spring hanger and 6-inch shackle (2-inches longer than stock), while the Dynatrac axle was mocked up with the spring perches to set pinion angle.
16. The RuffStuff perches were a perfect fit and even feature three options for locating the leaf center pins. Having the ability to choose the center-pin location makes it easy to alter the wheelbase and center the wheel in the wheelwell.
17. Next, the axle was moved into place and the Deaver Spring U-Bolts were installed through the RuffStuff U-bolt plates.
18. Here, the stout Dynatrac 60 axle hangs nicely under the newly modified frame.
19. To prevent corrosion on our raw metal, we coated the fresh welds with a little black chassis paint.
20. Our final step was to strip down the entire chassis and have the frame media blasted and powdercoated. With all the fab work complete and the frame wearing a fresh new coat of gloss black, we were ready to take it home and start the process of reassembly.