Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Four-Wheel Drive Systems - Overview
2021 Ford Edge SE, 4WDSECTION Four-Wheel Drive Systems - Overview
WARNING: This page is about a different car, the 2018 Ford F-550 Super Duty, 2018 Ford F-450 Super Duty, 2018 Ford F-350 Super Duty, and 2018 Ford F-250 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
Manual Shift-On-Stop (MSOS
The MSOS system consists of the following:
- Transfer case
- Transfer case shift lever
- Manual locking hubs (hublocks)
- Four-Wheel Drive (4WD) indicators in the IPC message center
- Shift linkage
- Mode Indicator Switch
Electronic Shift-On-The-Fly (ESOF) System
The electronic shift 4WD system consists of the following:
- Transfer case
- TCCM
- High Speed Controller Area Network (HS-CAN)
- Mode Select Switch (MSS)
- Transfer case shift motor
- 4WD indicators and 4WD system messages in the IPC message center
- Constant Vacuum Hublock (CVH)
- CVH solenoid and vacuum lines
- Vacuum pump (diesel engine only)
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.