SOA on an early Bronco is a serious fabrication project. Do not attempt this without welding skills and a proper shop environment. The result is a capable dedicated trail rig — not a comfortable street truck.
Spring over axle moves the leaf springs from below the axle housing to above it, using the full spring arch as lift rather than losing it under the axle. On an early Bronco with approximately 4.5" of spring arch, SOA yields ~8–10" of lift depending on spring selection.
**What SOA requires:**
1. **New spring perches:** The factory spring perches are under the axle. SOA relocates them to the top of the housing. This requires welding new perch pads to the top of each axle tube — precision work, since perch centerline must align with the axle centerline.
2. **Shackle reversal or extension:** The front shackle geometry changes with SOA. Some builders run a shackle reversal kit; others extend the factory mount. Each approach has handling tradeoffs.
3. **Driveshafts:** SOA dramatically increases driveshaft angles. A custom front driveshaft (Tom Woods, Dynatrac) is mandatory. The rear transfer case output angle changes enough to require an SYE (slip yoke eliminator) on the Dana 20 and a CV-style rear driveshaft.
4. **Steering geometry:** The steering drag link and tie rod are now at a different angle. A dropped pitman arm or a high-steer kit is required to prevent severe bump steer.
5. **Brake lines:** All brake lines must be custom-fabricated or extended. Safety-critical — no shortcuts.
6. **Shock mounts:** Factory shock mounts are at the wrong height and angle. New mounts must be welded.
**Typical SOA lift result:** 8–10" over stock. Fits 37–40" tires comfortably with proper offset wheels and fender trimming.
| Part | Vendor | Est. price |
|---|---|---|
| Custom spring perch plates (fabricated) | Fabricated | ~$80 |
| Tom Woods custom front driveshaft | Tom Woods | ~$420 |
| SYE (slip yoke eliminator) for Dana 20 | Various | ~$280 |
| Long travel shocks (extended/bypass) | King / Fox | ~$900 |
| Extended brake lines (full set) | Custom | ~$150 |
| Extended bump stops | Various | ~$60 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.