Realistic 4×4 Traction System V1.2.0.0

This mod adds a switchable 4×4 traction system to compatible tractors, trucks, harvesters and cars. It supports front-axle control, differential locking and automatic responses based on actual wheel slip.

Features

• Real rear-wheel slip detection: automatic modes react to actual wheel slip physics, not just speed.
• Four drive modes, assigned per vehicle out of the box:
• Manual: you are always in control.
• Semi-auto: engages on real slip, with manual override always available.
• Auto: the same logic, tuned for vehicles with factory-automatic 4WD (CVT/IVT drivetrains).
• Smart: Fendt-style continuous, proportional engagement with no hard on/off switching.
• Native tire pressure simulation on engagement with no dependency on any other mod.
• On-screen HUD with live status and adjustable position from the in-game Settings menu.
• Zero XML edits to any vehicle; the system injects itself into every compatible vehicle automatically.

Changelog

V1.2.0.0

MULTIPLAYER (tested on a real dedicated server):

• Differential detection on dedicated servers fixed; it previously always failed on the client side.
• Toggling 4×4 (Ctrl+J) now synchronizes correctly between the server and clients.
• Manual differential lock (Ctrl+K) now synchronizes correctly between the server and clients.
• Automatic modes (auto/semiauto/smart) are calculated by the server and synchronized with all clients.
• A player joining in the middle of a session immediately receives the correct state of every vehicle.

REALISM:

• Ctrl+K (manual differential lock) respects a speed limit for engagement; it only locks when stationary or moving slowly, just like in a real transfer case.

GENERAL:

• Internal diagnostic code removed.
• Documentation and store description reorganized.

V1.1.0.0

• Fendt Vario Grip Smart remains unchanged for now; more details on how it works are being reviewed.

New Features

Automatic differential lock

• In “Auto” and “Smart” drive modes, the center differential lock now engages and disengages by itself under severe wheel slip, at low speed only (never on the road).
• “Semi-Automatic” and “Manual” modes still require Ctrl+K.

Shop upgrade: Semi-Automatic → Automatic

• Tractors configured as “Semi-Automatic” now show a new configuration option in the store’s Customize screen, letting you pay to upgrade that specific unit to full “Automatic” behavior (automatic diff lock included).
• This was added because many players did not realize Semi-Automatic and Automatic tractors behave differently. The option is now labeled clearly:
• Semi-Automatic (Diff Lock Manual) — free, default.
• Automatic (Diff Lock Automatic) — paid upgrade.

Known Issues

• There are several things that may need a tweak or fix.
• Not all vehicles have real or near real specs.
• This was not tested in depth with other mods, including mod tractors or maintenance scripts except my maintenance mod, so compatibility is not fully confirmed with other mods yet.

Fixes Excluded

• Three grape harvesters with independent hydraulic wheel motors (ERO Grapeliner Series 7000, New Holland Braud 9070L, Gregoire GL) are excluded. These vehicles are always all-wheel-drive by design (four independent hydraulic motors, no mechanical differential to switch), so the mod no longer applies to them.
• Crawlers and tracked vehicles no longer get the 4×4 system.

Documentation

• The real difference between “Semi-Automatic” and “Automatic” modes was clarified in the in-game HUD hints, configuration comments and readme: both engage and disengage the 4×4 automatically based on real wheel slip; the actual difference is that only “Automatic” (and “Smart”) also lock the differential automatically.

Compatibility

• Singleplayer only.
• No changes to save-game compatibility; existing installs can update directly.

V1.0.1.0

• Keybinds changed to Shift+Ctrl+J/K/N to avoid conflicts with other mods.
• Auto/semi-auto response is much faster; confirm delay cut from 2.5s to 0.9s.
• The 2WD↔4WD switch in manual/semi-auto/auto is now a short smooth ramp instead of an instant on/off, with no more jolt or momentary speed loss when the front axle engages under load.
• Optional soft compatibility with Hyper Realistic Maintenance 2, if you also run it; fully standalone otherwise.