LEMON Manuals: Even more car manuals for everyone
Home >> Ford >> 2012 >> Mustang Base, 2D Coupe, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 714 (Four-Wheel Drive Systems) >> Diagnosis And Testing >> Four-Wheel Drive Systems - Vehicles With: Electronic Shift Transfer Case >> Pinpoint Tests >> Pinpoint Test E : The Front Axle Makes Noise In 2H Mode Only And Generally Under Heavy Throttle >> Notes

Pinpoint Test E : The Front Axle Makes Noise In 2H Mode Only And Generally Under Heavy Throttle: Notes

WARNING: This page is about a different car, the 2015 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

Refer to Two Wheel Drive/Four Wheel Drive Systems for schematic and connector information.

Normal Operation 

In 2H mode, the TCCM provides a ground path to the IWE solenoid to supply vacuum to each IWE (disengaging the front hubs from the front axle). During certain conditions such as WOT maneuvers, manifold vacuum is lower than desired. To maintain uninterrupted IWE function in 2H mode, stored engine vacuum is sourced from the vacuum reservoir. A one-way check valve is implemented between the manifold and IWE solenoid/vacuum reservoir to prevent the stored vacuum from escaping into the manifold during low engine vacuum conditions. For noise-free IWE operation under all conditions, the check valve must be operating correctly.

Possible Sources 

scientia non olet · About LEMON Manuals