An interactive, mechanically connected teaching model of a four-door off-road 4×4’s chassis and part-time drivetrain, built from published specifications. It is not factory CAD, a service manual or a vehicle-dynamics simulation.
Start with a question
Select 01 Open differential. The left output is held at zero and the right turns twice as fast as the case. Then select 02 Lock & low range: the lockers engage, both outputs match, and the transfer output falls to a quarter of its input.
Select 03 Cross-axle articulation and watch each rigid axle move with its control arms, track bar, coils, dampers and propshaft; toggle the front anti-roll bar. Then select 04 Steering linkage, turn the wheel and follow the column, gear, pitman arm, drag link, knuckles and tie rod.
Reference configuration
2023 four-door reference vehicle, left-hand drive, 3.6-litre V6 with the six-speed manual, a part-time two-speed transfer case (not the optional full-time unit), solid beam axles front and rear with selectable electric lockers and 4.10:1 gears, and LT285/70R17C all-terrain tires on 17 × 7.5 wheels. Published figures used directly: 3,008 mm wheelbase, 1,636 mm track, 4.0:1 low range, 15.6:1 overall steering ratio with 3.2 turns lock to lock, 330 × 28 mm vented front and 342 × 14 mm solid rear discs.
Finishes follow the vehicle: black frame and suspension steel, satin black axle housings with bare cast-iron knuckles, a bare aluminium transfer case, red monotube shock bodies under black shrouds, machined wheels with black-painted pockets and red tow hooks. The body, interior trim, exhaust and wiring are left out.
Implemented mechanical relationships
The input gear turns the sun of a planetary set whose annulus is held by the case. In high range the range sleeve locks the mainshaft to the input gear (1:1); in low range it locks it to the planet carrier, which turns at a quarter of input speed. In 4H and 4L the mode sleeve locks the drive sprocket to the mainshaft and a silent chain turns the lower, driver-side front output at the same speed. There is no center differential: the two propshafts are locked together.
Each propshaft turns a hypoid pinion, and the ring gear on the differential case turns at pinion speed divided by 4.1. The front axle is a high-pinion, reverse-cut set with its ring gear on the passenger side of the pinion; the rear is a standard set with the ring on the driver’s side, so propshafts turning the engine’s way drive both axles forward. ωL + ωR = 2ωcase for an open differential; a locker dogs one side gear to the case, so ωL = ωR = ωcase.
On the 2023 reference vehicle with the part-time case, a front axle disconnect on the passenger-side tube opens in 2H so the front differential and propshaft can stand still, and closes in 4H and 4L. The bench has no road, so nothing back-drives the front axle.
Tooth counts and meshing
The 4.10:1 ring and pinion is 41/10: a listed count for the rear axle, and the only whole-number set with a ten-tooth pinion for the front. The side gears and pinion mates (16/10, two mates) and the planetary (24 sun, 72 annulus, four 24-tooth planets) are reconstructions because their counts are not published, but a simple planetary gives exactly 4.0:1 only with annulus = 3 × sun and planet = sun. Equal chain sprockets (37 teeth, modeled) are what 1:1 requires.
Every gear is phased so that teeth sit in spaces at the pitch point, and every angle on screen is the exact tooth ratio of its driver, so meshes never drift. The spider and planetary sets meet their assembly conditions, and the ring and pinion tooth lines and normal pitch agree at the mean contact point; the model build checks all of these.
Spur and helical teeth are involute, and bevel teeth use Tredgold’s back-cone approximation. Hypoid teeth are spiral-bevel forms placed at the hypoid offset, not the conjugate surfaces a gear generator would cut. The worm lead and sector radius of the recirculating-ball steering gear reproduce the published overall ratio with the modeled linkage.
Accuracy boundaries
Kinematic, not physical: shaft speeds are constrained, not produced by tooth contact. There is no torque, traction, tire, compliance, backlash, oil or synchronizer dynamics; the universal joints articulate without their velocity ripple; and the left/right speed-difference control prescribes output speeds, not friction.
Reconstructed: suspension, steering and frame hardpoints, housing castings, the transfer-case layout and offsets, the hypoid offset, and the engine and transmission envelopes. The five-link axles are solved from rigid link lengths with a small bush compliance whose residual is shown, and the knuckles steer about vertical axes.
Bench rules: lockers engage only in 4L, rear before front; the anti-roll bar disconnects only in 4L; the connected bar limits the commanded front articulation. These are teaching rules, not driving instructions, and the factory’s rules differ by year and trim.
Operation
Select the 3D view to use keys: Space runs or pauses, R returns to the chassis, 1–6 choose views, arrows orbit, + and − zoom, Esc releases the view. Drag to orbit, right-drag or Shift-drag to pan, and pinch or use Ctrl/⌘ + wheel to zoom.
Export bench state saves the settings, speeds and closure residuals as JSON; the image button saves the 3D view as a PNG.
Primary sources consulted
Manufacturer — 2023 vehicle specifications: wheelbase, track, tires, the transfer case’s 4.0:1 low range, axles and lockers, steering ratio, brakes and shocks.
Manufacturer — model capability overview: transfer case, selectable lockers and the electronic sway-bar disconnect.
Axle supplier — ring and pinion gearing: front and rear gear sets.
Sources checked 22 September 2026. Independent educational exhibit; not affiliated with any vehicle manufacturer or supplier.
