No 3-4 Shift
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2002 Lincoln Navigator, 2002 Ford Expedition, 2001 Lincoln Navigator, 2001 Ford RV Cutaway, and 2001 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
Improperly torqued valve body bolts (gasket damage), SS1 and/or SS2 failure to operate correctly, valve body components (overdrive accumulator regulator valve), 3-4 shift valve, overdrive one-way clutch assembly, overdrive clutch assembly and overdrive planet assembly.