In APM on PC, “4H” usually means 4 high on the drivetrain, and the PC keybind mentioned in one of the APM tutorials is N. In that tutorial, the creator also says you need to shift out of 2L or 4L to stop being locked in first gear and get back to normal driving speed.

How to do it

  1. Get in the vehicle.
  2. Press N to cycle the drivetrain mode.
  3. Keep pressing until you reach 4H.
  4. If you’re stuck in first gear, make sure you are not in 2L or 4L anymore.

What 4H does

  • 4H means four-wheel drive in high range.
  • It is meant for regular off-road driving where you want traction but still need speed.
  • The same tutorial explains that 2H and 4H let you keep accelerating normally, while low range modes keep you limited to first gear.

Small note

That source is a gameplay tutorial video, so the exact control layout can change after updates, but N is the clearest PC key mentioned for this APM drivetrain control.