VIBRATION - FELT THROUGH SEAT, FLOOR AND/OR STEERING WHEEL AT HIGHWAY SPEEDS WHILE IN 4TH OR 5TH GEAR - COBRA MODEL ONLY
Publication Date: APRIL 12, 2001
This article is being republished in it's entirety to update the service parts and to update the service procedure.
A vibration may be felt through the seat, floor and/or steering wheel at approximately 65 mph in 4th or 5th gear on some Mustang Cobra vehicles. This may be caused by a driveline vibration that is not properly isolated.
Install a revised rear axle damper and road test to verify condition has been corrected. Re-indexing the driveshaft may also be necessary based on the road test results. Refer to the following Service Procedure for details.
DO NOT USE THIS SERVICE PROCEDURE TO REPAIR OTHER CONDITIONS THAT DO NOT MEET THE ABOVE DESCRIPTION.
DO NOT CONFUSE DRIVELINE VIBRATION WITH A WHEEL AND TIRE VIBRATION OR CONVERTIBLE SHAKE WHICH STARTS AT A LOWER SPEED AND CAN BE FELT THROUGH THE STEERING WHEEL.
INSTALLING THE DAMPER WITHOUT INDEXING THE DRIVESHAFT MAY NOT COMPLETELY ELIMINATE THE VIBRATION.
THIS SERVICE PROCEDURE REQUIRES THE USE OF AN ELECTRONIC VIBRATION ANALYZER (EVA) ROTUNDA PART NUMBER 014-00344.
Road test the vehicle with the customer if necessary to verify the condition. If the suspect vibration can be felt, perform the following procedure.
Raise vehicle on a hoist.
Support the rear differential with a screw type jack stand and remove the two differential mount insulator bolts from the front of the rear differential. Discard the insulators (Figure 1).
Install new damper (1R3Z-4A263-AA) and new differential mount insulators (2 upper F3SZ-4B424-A, 2 lower F3SZ-4B431-B). Torque bolts to 70 N-m (52 lb-Ft) (Figure 2).
CHECK FOR DRIVELINE VIBRATION:
Install the magnet on the EVA pickup sensor and place the sensor on the damper bracket as shown (Figure 3).
Route the sensor wire into the passenger compartment, making sure it is away from the exhaust system and the drive shaft. Connect the sensor wire to the meter at the port marked "A".
Connect the EVA power cord into the cigarette lighter and press the Hz button (button #0) to set the meter to the Hertz (Hz) scale.
Drive the vehicle on an interstate highway in 5th gear at 65 mph. Allow a few seconds for the EVA readings to stabilize. Look for a frequency reading of 46-48 Hz. If a 46-48 Hz reading is present, record the amplitude (G's) of the vibration.
Repeat the test at 70 mph, (50-52 Hz) and at 75 mph, (54-56 Hz) Record the vibration amplitude at these speeds. Disregard any frequencies that are not within the 46-52 Hz range. They are not driveline related.
IF AN AMPLITUDE READING (G'S) HIGHER THAN 0.17 IS DETECTED AT ANY OF THESE 3 SPEEDS, THE DRIVESHAFT MUST BE INDEXED ON THE TRANSMISSION OUTPUT SHAFT.
INDEXING THE DRIVESHAFT TO THE TRANSMISSION OUTPUT SHAFT:
Verify that the yellow paint dot at the rear of the driveshaft is in alignment with the yellow paint dot on the axle flange. If it is not, align it and road test the vehicle again (Figure 2).
Locate the yellow paint dot at the front of the driveshaft near the slip yoke.
Remove driveshaft bolts and rotate the driveshaft so that the front yellow dot is on the bottom (6 o'clock position) (Figure 4).
Pull the driveshaft out of the transmission.
Use a paint pencil or office correcting fluid (White-out) to paint a reference mark at the end of the transmission output shaft at the 6 o'clock position and allow a few minutes to dry (Figure 5).
Rotate the transmission output shaft 1/4 of a turn (90 degrees) so that the dot is at the 9 o'clock position (Figure 6).
Re-install the driveshaft into the transmission, maintaining the yellow dot at the 6 o'clock position.
Re-install the driveshaft at the rear axle. Make sure rear dots are in alignment.
Road test the vehicle again and record the amplitude of the vibration, compare the new readings to the previous.
Continue re-indexing the driveshaft at the transmission output shaft until the lowest level of vibration is identified. Return the driveshaft to the position of the lowest amplitude reading. Paint a new mark on the transmission output shaft to align with the driveshaft yellow dot for future reference (Figure 7).
Road test the vehicle to verify the repair.
Damper - Rear Axle
Insulator - Rear Axle Upper - 2 Required Per Vehicle
Insulator - Rear Axle Lower - 2 Required Per Vehicle
OTHER APPLICABLE ARTICLES:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage
Replace Rear Axle Damper (Includes Time To Test And Re-index Driveshaft)