Front Axle Selection for an Astro SFA Conversion
A structured comparison of common donor front axles — with the values that actually determine fit, not marketing claims.
Selection criteria
Before comparing part numbers, list what actually matters for your build:
- WMS-to-WMS width — must match your target track width and body clearance.
- Differential drop side — determines which side the front driveshaft exits and whether it clears the oil pan.
- Pinion location (high or low) — high pinion improves driveshaft angle in a lifted rig.
- Lug pattern & wheel offset — must match rear axle and wheel package.
- Brake size — determines caliper/rotor availability and hydraulic balance.
- Steering-knuckle style — determines what steering arms and joints will bolt on.
- Parts availability — long-term serviceability including seals, ball joints, U-joints, and gears.
Candidate comparison
All values below are typical starting points, not commitments. Verify against the donor axle in front of you.
| Candidate | Typical WMS | Diff drop | Pinion | Notes / risks |
|---|---|---|---|---|
| Narrow-track Wagoneer / Grand Wagoneer Dana 44 (1980–1991) | ~60 in WMS-to-WMS typical — verify per donor | Typically driver-side drop, spring-under — verify per donor | Low-pinion (front use) | Common SFA donor. Ball-joint kingpin variants differ. Disconnect (vacuum-shift) housings and other year-to-year variations exist — measure and identify every donor. Pre-1980 Full-Size Jeep front axles may be passenger-side drop; donor year matters. Reject bent or previously repaired housings. |
| Other Dana 44 (Ford / GM HP) | Verify | Verify | Some are high-pinion | High pinion helps driveshaft angle in a lifted van. Confirm knuckle-arm attachment style. |
| Dana 60 (various) | Wider — verify | Verify | Both HP & LP exist | Heavier, wider, stronger. Consider only if tire/payload plan justifies the weight and packaging. |
Stop-work · No universal 'X handles 35s easily' claim
Donor inspection checklist
- Confirm axle type by casting mark, tag, or ring-gear diameter — not by the seller’s claim.
- Measure WMS-to-WMS (not backing plate to backing plate).
- Rotate pinion by hand; feel for roughness, backlash, and preload loss.
- Pop the diff cover — inspect ring & pinion wear pattern and identify the carrier / locker installed.
- Check kingpin/ball-joint condition, knuckle bore, and steering arm mounting.
- Inspect axle tubes for previous welding, straightening, or heat damage.
- Check brake components: caliper mount type, rotor size, hose fitting size.
Applicability & program status
The reference program targets a narrow-track Dana 44 candidate. Final selection is deferred until at least one donor axle is inspected in person. See the Reference Build journal.
What we know
- • Different Dana 44 variants have meaningfully different pinion locations, knuckle styles, and diff-drop sides.
- • 1980–1991 narrow-track Wagoneer / Grand Wagoneer Dana 44 is generally a driver-side-drop, spring-under front axle, commonly cited around 60 in WMS-to-WMS — still measure every donor.
- • Pre-1980 Full-Size Jeep front axles may be passenger-side drop; donor year matters.
Proposed design targets
- • Program leans toward a narrow-track Dana 44 candidate with driveshaft-angle-friendly geometry, subject to donor measurement.
Must be verified before fabrication
- • Actual WMS target based on measured Astro frame width and wheel/tire package.
- • Donor axle inspection reports — none on file yet.
- • Whether the donor housing is a disconnect-style variant.
Verified sources
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