Some 2005-2009 Mustangs (except the GT500) equipped with either a 4.0L or 4.6L engine may exhibit a heavy driveline shudder on acceleration from a stop, or between 3-15 mph. On 4.0L engines, there may also be an above-average engine presence.
The wrong transmission crossmember assembly may have been installed at the factory. Similar complaints may also occur if the transmission crossmember and transmission support insulator were improperly reassembled after transmission removal.
Inspect the transmission crossmember assembly orientation (Figure 1). On 4.6L-equipped vehicles, the transmission crossmember hump should extend upward. The support insulator should feature a white or yellow paint dot. On 4.0L-equipped vehicles, the transmission crossmember hump should extend downward. The support insulator mount should feature a blue paint dot.
If present, remove and discard exhaust mounts and isolators from the transmission crossmember. These are production assembly aids and are not required. Do not cut the hanger rod from the exhaust system.
Orient the crossmember to match the engine at hand. Install a new engine-specific transmission support insulator mount onto the transmission crossmember. Torque the support insulator mounting nuts to a value of 52 ft-.lb.
Bend the exhaust hanger rods to a horizontal position to create approximately two inches clearance to the transmission crossmember (Figures 2 and 3).
Verify that the exhaust system is properly aligned by measuring the distance between the exhaust pipe and floor pan (behind the catalytic converter). The distance should be two inches, +/- 0.5 inch.
Ford Part numbers for new transmission support insulator mounts are as follows:
4.0L engine 8R3Z-6068-D
4.6L engine 8R3Z-6068-E