VIBRATION/SHAKE - AT STEADY SPEED APPROXIMATELY 100 KM/H (62 MPH) - VEHICLES WITH 4.6L ENGINE AND CONVERTIBLE TOP
Publication Date: APRIL 25, 2000
A vibration/shake while driving at a steady speed of approximately 100 km/h (62 mph) on smooth roads may occur on some vehicles. This may be due to the interaction between the body and suspension modes.
Perform Steps 1-7 of the Service Procedure to insure the vibration is not due to any common cause condition. If vibration is still unacceptable, install the components listed in this TSB article to reduce the vehicle's sensitivity to vibration. Refer to the following Service Procedure for details.
Verify the tires are not flat spotted, out of round, or excessively worn and the rims are not damaged or untrue.
Set all tire pressures to the pressure recommended on the vehicle label.
Verify that the lateral and radial runout of the wheel is less than 1.14mm (0.045"), then check to make sure the tires are properly balanced on a calibrated tire balancer.
Normalize engine and transmission mounts to eliminate possible stressed or bound up conditions.
Check for loose suspension fasteners, control arms, steering rack, engine mounts, crossmember, etc.
Replace any worn suspension or steering components.
Re-evaluate the vehicle. If OK, return to the customer. Some Mustang convertibles may be more sensitive to vibration than others. If unacceptable vibration is still detectable, perform the remaining Steps of this TSB.
Remove the negative battery cable.
Replace the engine mounts with a new set of Engine Mounts (XR3Z-6038-DA - RH and XR3Z-6038-DB - LH; these mounts are of a higher stiffness). Refer to the 1998 Mustang Workshop Manual for replacement procedure.
Install a set of Underbody Rails (XR3Z-76101W09-AA - Left and XR3Z-76101W08-AA - Right). Refer to Figure 1 to determine where to place the rails to the underbody. The underbody rails will need to be welded to the underbody of the vehicle by referring to the following:
A Mig welder and standard body Gas Metal Arc Welding repair procedure should be used. Remove the paint in the welding area only for better weld penetration.
The welds should have a minimum 5mm weld bead and a minimum total length of 75mm on both sides of the rail and at both front and rear ends (Figure 2).
Upon completion, the welded area should be treated for corrosion using Super Sealant (F3AZ-19515-SA or equivalent).
If this vehicle has an automatic transmission, transfer the attaching shift cable retainer from the body to the bracket that is located on the underbody rails.
Replace the Rear Shocks (F8ZZ-18125-BB; refer to the 1998 Mustang Workshop Manual, Section 204-02) using the new upper mount hardware included in the kit. Replace theFront Struts (F8ZZ-18124-BB; refer to the 1998 Mustang Workshop Manual, Section 204-01) using the new upper mounting hardware that is included in the kit. Reuse the existing jounce bumper and dust shield. The new mounting hardware includes as part of the fix a higher rate (stiffer) rubber isolator (white mark) and a 2mm shorter steel spacer.
Reconnect the battery.
Underbody Rail - Left
Underbody Rail - Right
Engine Mount - RH
Engine Mount - LH
OTHER APPLICABLE ARTICLES:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage