10.7 - Steering¶
Type: Full hydraulic steering
Manufacturer: PSC Motorsports
Full hydraulic steering with no mechanical linkage: a PSC pump feeds a PSC orbital steering control valve, which drives a double-ended ram. Ram stroke is limited by steering stops set to the u-joint bind angle and ram travel, and the ram mounts on a Barnes 4WD universal DIY ram mount to Offroad Anonymous weld-on high steer arms on the Super Duty Dana 60 (see Front Axle). A Mishimoto fluid cooler with fan (gated by a 180 °F inline thermostat) cools the circuit.1
Component part numbers below come from the PSC FHK400TJ kit — the 1997-2006 TJ/LJ Extreme Series full hydraulic kit with a 2.75" double-ended cylinder (PSC's 40"+ tire kit).2 The orbital valve and cylinder carry over directly; the kit pump is the exception — its PK40JP2-FH bracket is Jeep 4.0L-specific and does not fit this build's Cummins R2.8.
Specifications¶
| Component | Specification |
|---|---|
| Type | Full hydraulic (no mechanical linkage) |
| Kit | PSC FHK400TJ (TJ/LJ Extreme Series, 2.75" double-ended) |
| Steering Control Valve | PSC 160cc orbital (in FHA160-S accessory kit) |
| Ram | PSC SC2227K1 (2.75" × 8.0" double-ended) |
| Pump | Cummins-specific PSC pump — TBD #99 (kit PK40JP2-FH is 4.0L-only) |
| Reservoir | Remote (included with pump kit) — model TBD #103 |
| Cooler | Mishimoto fluid cooler + fan (180 °F inline thermostat) |
| Fluid | PSC 715 (SWEPCO 715) |
System Components¶
Hydraulic Pump¶
Pump is engine-specific — the kit pump does not fit. The FHK400TJ kit ships a PK40JP2-FH pump kit built for the Jeep 4.0L accessory drive. This build runs a Cummins R2.8, so the kit pump/bracket does not bolt up — a Cummins-compatible PSC pump must be sourced. The kit's orbital valve and cylinder are engine-agnostic and carry over unchanged.
| Specification | Value |
|---|---|
| Manufacturer | PSC Motorsports |
| Model | TBD #99 — Cummins R2.8 pump + bracket (NOT the kit's PK40JP2-FH) |
| Flow Rate | TBD #99 |
| Pressure | TBD #99 |
| Drive | TBD #99 (belt vs. Cummins gear-drive) |
Steering Control Valve¶
| Specification | Value |
|---|---|
| Type | Orbital (PSC) |
| Model | 160cc — supplied in PSC FHA160-S accessory kit |
Steering Ram¶
| Specification | Value |
|---|---|
| Type | Double-ended (PSC) |
| Model | SC2227K1 |
| Bore | 2.75" |
| Stroke | 8.0" native; effective stroke set by steering stops (40 degree target, see Front Axle) |
| Mount | Barnes 4WD universal DIY ram mount; ORA 05-16 SD60 full hydro high steer arms (see Front Axle) |
Reservoir¶
| Specification | Value |
|---|---|
| Type | Remote (included with PSC pump kit) |
| Capacity | TBD #103 |
| Location | TBD #103 |
Cooler¶
| Specification | Value |
|---|---|
| Unit | Mishimoto fluid cooler |
| Fan | Mishimoto (matched to cooler) |
| Control | 180 °F inline thermostat |
| Fan Current Draw | TBD #101 (confirm fits PMU Out 8 ~15A budget) |
| Fan Power Source | PMU Out 8 (~15A, thermostat-switched) — see PMU Outputs |
Fluid Specifications¶
| Specification | Value |
|---|---|
| Fluid Type | PSC 715 (SWEPCO 715) |
| Capacity | TBD #103 (kit ships ~4 qt; confirm system fill) |
Outstanding Items¶
🔴 Critical (1)
- Rear 5.13 long-spline gearset (Revolution F10.25-513L) sourcing confirmation (#297) — There is no 10.5-native 5.13; the rear Sterling 10.5 runs the Revolution F10.25-513L (Ford 10.25" long pinion) with master kit 35-2046. Confirm availability and lead time with Revolution or a dealer before ordering the kit. A 2008-2010 donor housing also needs the SK F10.5-Conv pinion spacer (sold separately).
High (8)
- Re-spec 8HP70 → NP241OR adapter path (case changed from JK NV241 to TJ Rubicon Rock-Trac) (#313) — The transfer case selection changed from the JK NV241 GenII Command-Trac (2.72:1) to the TJ/LJ Rubicon NP241OR Rock-Trac (4:1) (owner decision, 2026-09-18 — deeper low range). All the adapter research on the transfer-case page was done against the JK case and does not carry over automatically.
- iBooster pedal ratio verification against 1.25" booster stroke (#301) — Verify the brake pedal ratio (approximately 4:1 per owner notes, 03-06 TJ/LJ auto pedal) against the Bosch Gen 2 iBooster's 1.25" stroke so the pedal reaches full booster travel without the cylinder bottoming, with the 1-1/8" Wilwood master and Super Duty calipers at all four corners. Bench-measure on assembly.
- ARB RD140 fitment with Revolution F10.25-513L in the Sterling 10.5 housing (#300) — The rear runs a 10.25" ring gear (Revolution F10.25-513L) in the 10.5 housing with the ARB RD140 carrier (Ford 10.25/10.5, 35 spline, all ratios). Confirm with ARB or Revolution that the RD140 flange and ring gear bolt pattern match the F10.25 gear in this housing before ordering, and confirm the pinion depth starting point (owner note: add roughly 0.120" to the pinion depth stack).
- Ball joint delete clearance against ORA high steer arms (#299) — Verify the American Iron ball joint delete (upper and lower, welded) clears the Offroad Anonymous 05-16 Super Duty Dana 60 weld-on full hydro high steer arms through full steering travel (40 degree target with the 8" PSC ram) and full suspension travel.
- Front axle ball joint delete bushing offset (0 / 1.5 / 3 degree) (#298) — American Iron ball joint delete bushing offset sets caster and camber together, summing to the bushing rating. Select after caster is measured with the Dana 60 under the vehicle at ride height. Every 15 degrees of bushing rotation gives 0.5 degrees of change on a 3-degree set.
- 4WD/4LO indicator — NP241OR position switch → PMU → HDX (measure switch at teardown) (#145) — Reversed 2026-09-18 — the 4WD indicator is wanted after all. (Previously closed as "omit the indicator.") Updated the same day for the transfer-case change from JK NV241 to TJ/LJ Rubicon NP241OR (#313), which makes this easier.
- Turbolamik Aux: P/N (#48) — Confirm aux output channel + pinout configured for P/N (start interlock)
- Turbolamik Aux: Reverse (#47) — Confirm aux output channel + pinout configured for Reverse signal -> PMU In 3
📋 Medium (9)
- ABS sensor opening plugs, front and rear axles (#310) — With no ABS on the build, the tone rings are omitted and the wheel speed sensor openings must be plugged. An unplugged opening in the rear housing is a gear oil leak path.
- Confirm ORA high steer kit quantity (per arm vs per pair) (#302) — Confirm whether the Offroad Anonymous 05-16 Super Duty Dana 60 weld-on full hydro high steer kit is sold per arm or per pair before ordering, so the purchase tracker quantity is right.
- Steering Cooler Fan (electrical) (#101) — On PMU Out 8 (~15A, 180F inline thermostat); confirm actual Mishimoto fan draw fits budget
- Steering Pump Specs (#99) — Kit pump PK40JP2-FH is Jeep 4.0L-only - source Cummins R2.8 PSC pump/bracket; flow/pressure/drive TBD
- Rear Suspension Components (#98) — Coil rate, bypass valving, control arms, track bar, sway bar
- Front Suspension Components (#97) — Coil rate, bypass valving, control arms, track bar, sway bar
- Rear Driveshaft Specs (#94) — Custom (Tom Woods) decided - measure length at final ride height & order
- Front Driveshaft Specs (#93) — Custom (Tom Woods) decided - measure length at final ride height & order
- Transmission Pilot Bearing (#91) — If required by flywheel/crank combination
📝 Low (2)
- Steering Reservoir & Fluid (#103) — Fluid = PSC/SWEPCO 715; remote reservoir (in pump kit) model/location + system fill qty TBD
- Suspension Geometry (#102) — Departure and breakover angles (calculated from chosen suspension)
Build Tasks¶
- Source a Cummins R2.8-compatible PSC pump + bracket (kit PK40JP2-FH is 4.0L-only)
- Confirm pump drive type (belt vs Cummins gear-drive), flow rate, and pressure
- Confirm remote reservoir model and mounting location
- Confirm fluid system fill quantity
- Confirm Mishimoto cooler fan current draw fits the PMU Out 8 (~15A) budget
- Document hydraulic line routing
Related Documentation¶
-
Owner decision, 2026-05-30 — full-hydro kit is PSC pump + PSC orbital valve + PSC double-ended ram; Busted Knuckle Off-Road steering stops limit ram stroke to Dana 44 spec; Artec Industries Dana 60 ram mount cut down to the Dana 44; Mishimoto fluid cooler + fan on a 180 °F inline thermostat. Model numbers, bore/stroke values, flow/pressure, and fluid specs remain pending. Updated 2026-09-16 with the Dana 60 front: the Busted Knuckle stops and the cut-down Artec mount are superseded by the Barnes 4WD universal mount and ORA high steer arms (see Front Axle). ↩
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PSC Motorsports FHK400TJ — 1997-2006 Jeep TJ/LJ Extreme Series full hydraulic kit, 2.75" double-ended cylinder (PSC Motorsports / pscsteering.com, accessed 2026-05-31). Kit boxes: FHA160-S (160cc full-hydraulic accessory kit w/ orbital valve), PK40JP2-FH (high-flow pump kit — Jeep 4.0L bracket, not used here), SC2227K1 (2.75" × 8.0" double-ended cylinder); fluid PSC/SWEPCO 715. Smaller-tire variant is FHK100TJ (2.5" bore / 125cc valve, 35-42"). Pump bracket is 4.0L-specific, so it does not fit this build's Cummins R2.8 — valve and cylinder carry over. ↩