10.1 Transmission - ZF 8HP70 (845RE)¶
Type: 8-speed automatic transmission
Model: ZF 8HP70 (Chrysler 845RE)
Donor Vehicle: 2015-2019 RAM 1500 EcoDiesel 4x4
Torque Capacity: 520 lb-ft (factory), 700+ lb-ft (built)
Controller: Turbolamik TCU 2.0 with basic wiring harness
Adapter Kit: Custom (in progress)
Specifications¶
| Specification | Value |
|---|---|
| Manufacturer | ZF Friedrichshafen |
| Model | 8HP70 (Chrysler 845RE) |
| Donor | 2015-2019 RAM 1500 EcoDiesel 4x4 |
| Type | 8-speed automatic, 4WD |
| Torque Capacity | 520 lb-ft (stock) |
| Weight | ~225 lbs (dry) |
| Length | ~27.5" |
| Fluid Capacity | ~9 quarts (pan drop service) |
| Fluid Type | ZF Lifeguard 8 (or equivalent) |
Gear Ratios¶
| Gear | Ratio |
|---|---|
| 1st | 4.714 |
| 2nd | 3.143 |
| 3rd | 2.106 |
| 4th | 1.667 |
| 5th | 1.285 |
| 6th | 1.000 |
| 7th | 0.839 |
| 8th | 0.667 |
| Reverse | 3.295 |
Controller - Turbolamik TCU 2.0¶
Model: Turbolamik TCU 2.0
Variant: Basic Wiring Harness (CAN)
Product Page: Turbolamik TCU 2.0
Manual: Turbolamik Manual
| Specification | Value |
|---|---|
| Supported Trans | 8HP45, 8HP50, 8HP55, 8HP70, 8HP75, 8HP90, 8HP95 (Gen1/Gen2/Gen3) |
| Shift Speed | 50-150ms |
| Drive Modes | 8 configurable (Street, Race, Offroad, etc.) |
| CAN Protocols | ECUMaster, Haltech, AEM, Motec, MaxxECU, etc. |
| Transbrake | Yes |
| Virtual Clutch | Yes |
| Price | ~€1,880 (~$2,000) with basic harness |
Why Turbolamik over MaxxECU:
- Supports all 8HP generations (MaxxECU is Gen1 only)
- Works standalone with Cummins ECM (no torque reduction dependency)
- Proven ECUMaster CAN integration (compatible with PMU24)
- 10+ years development, not beta
Electrical Requirements¶
Power¶
| Circuit | Wire Gauge | Source | Destination | Notes |
|---|---|---|---|---|
| TCU Power | 12 AWG | START+ Forward Dist Bus (25A CB) | Turbolamik harness (1.8m) | 15A, CONSTANT (must stay on); relocated off PMU OUT16 |
| TCU Ignition | 18 AWG | Ignition bus | Turbolamik harness | Wake-up signal |
| TCU Ground | 14 AWG | Engine bay ground bus | Turbolamik harness | 700mm lead from harness |
Note: TCU power must remain active at all times - if power is cut before TCU goes to sleep, adaptations won't save.
CAN Bus Integration¶
| Connection | Wire Gauge | Source | Destination | Notes |
|---|---|---|---|---|
| CAN H | 20 AWG | Turbolamik harness | Cummins J1939 tap | Twisted pair with CAN L |
| CAN L | 20 AWG | Turbolamik harness | Cummins J1939 tap | Twisted pair with CAN H |
The Turbolamik communicates with the Cummins R2.8 ECM via J1939 CAN for:
- Engine RPM
- Throttle position
- Vehicle speed
CAN Tap Location: Same tap point as PMU24 and Dakota Digital (Cummins body harness)
Sensors & Inputs¶
| Sensor/Input | Type | Notes |
|---|---|---|
| Input Speed Sensor | Internal to trans | Hall effect |
| Output Speed Sensor | Internal to trans | Hall effect |
| Transmission Temp | Internal to trans | NTC thermistor |
| Range Sensor (BTSI) | Internal to trans | Gear position |
| Shifter Input | Electronic shifter | Kilduff (factory 8HP70 connector) |
| Brake Switch | Digital input | Unlock from Park |
Aux Outputs (TCU → Vehicle)¶
| Output | Function | Destination | Notes |
|---|---|---|---|
| Aux Out (Reverse) | 12V when shifter in R | PMU In 3 | Drives PMU OUT22 (Reverse Lights) |
| Aux Out (P/N) | 12V when shifter in P or N | [Reserve] | Not currently consumed; PBS-I handles brake interlock for cranking. Available for future P/N gating if needed. |
| J1939 broadcast | Gear position, trans temp, mode | BIM-01-2 J1939 → HDX GEAR | Shares Cummins J1939 bus |
Shifter¶
Model: Kilduff 8HP70 / 8 Speed ZF Shifter for Swaps
Finish: Red with Skulls
Product Page: Kilduff 8HP70 Shifter
| Specification | Value |
|---|---|
| Dimensions | 10" L × 4.5" W × 5" H |
| Handle Height | 11" (tallest) |
| Type | Electronic (no cables) |
| Positions | P-R-N-D, +/- manual |
| Connection | Factory 8HP70 connector |
| Mounting | Center console |
Manual Mode (+/-): Allows manual gear selection for rock crawling, engine braking on descents, and technical terrain.
Wiring: Electronic shifter connects directly to transmission controller. No shift cables required.
Drive Mode Switch¶
| Specification | Value |
|---|---|
| Type | Rocker switch (SPDT or 3-position) |
| Location | Dash rocker switch panel |
| Connection | Transmission controller mode input |
| Position | Mode | Use Case |
|---|---|---|
| Up | Sport | Higher shift points, firmer shifts |
| Center | Normal | Daily driving, highway |
| Down | Tow/Haul | Engine braking, grades, towing |
Wiring: Low-current signal wires from rocker switch to transmission controller mode input pins. Exact pinout depends on controller selection (Compushift vs US Shift).
Cooling¶
| Component | Notes |
|---|---|
| Trans Cooler | External cooler recommended |
| Cooler Lines | -6 AN or factory hard lines |
| Thermostat | 180°F bypass thermostat recommended |
Adapter & Bellhousing¶
| Component | Source/Part Number | Notes |
|---|---|---|
| Adapter Kit | Custom | R2.8 to 8HP70 (in progress) |
| Flexplate | Adapted from AX15 kit | R2.8 to 8HP70 (custom adapter) |
| Pilot Bearing | TBD #91 | If required |
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¶
- Order Turbolamik TCU 2.0 with basic wiring harness
- Install Turbolamik TCU on 8HP70 mechatronic (soldering required)
- Route TCU power from START+ Forward Distribution Bus (12 AWG, 25A CB, CONSTANT)
- Connect TCU CAN to J1939 bus (same tap as PMU/Dakota Digital)
- Install Kilduff shifter in center console
- Wire drive mode rocker switch (dash panel) to TCU mode inputs
- Complete custom adapter kit for R2.8 to 8HP70
- Complete flexplate adaptation from AX15 kit
- Determine transmission cooler size and routing
Related Documentation¶
- Transfer Case - NP241OR connection (adapter re-spec pending)
- PMU Inputs - J1939 CAN bus tap
- Cummins R2.8 - Engine CAN integration