Full-time (permanent) 4WD
Also called: permanent 4WD, AWD
Full-time 4WD drives all four wheels continuously through a center differential, so it is safe to leave engaged on any surface, including pavement.
How it works
All four wheels are driven continuously. A center differential allows the front and rear axles to turn at slightly different speeds, so it can be used on any surface including pavement.
When to use it
Any surface, set-and-forget. Continuous traction without engaging anything.
Pros and cons
Pros
- Always-on traction
- Pavement-safe
- Nothing to engage
Cons
- Heavier and thirstier
- More complex
- Uncommon on kei trucks
Compared to other systems
Against part-time 4WD: pavement-safe and simpler to drive, but heavier and less efficient. Rare on kei trucks, which mostly use part-time systems.
Why you will rarely see this on a kei truck
Full-time 4WD solves the one real annoyance of part-time systems — you never have to think about engaging it, and it is safe on the road at all times. So why is it almost absent from the kei truck world? Weight, cost, and complexity. A center differential and the hardware to drive all four wheels continuously add mass and expense to a vehicle whose entire purpose is to be small, light, and cheap to run.
If you do come across a kei truck advertised with a full-time system, treat it as the exception rather than the rule, and budget time to understand exactly what you are buying — it will be a less common configuration for mechanics outside Japan to have seen before, which can matter when something eventually needs attention.
Models with this drivetrain
Trim-level mappings for this drivetrain are still being verified — confirmed models will appear here once the data is checked against factory spec sheets.