Suspension - Vibration/Droan at 55-75 MPH
No.: LTB00083Issue: 1
Date: October 4, 2007
THIS BULLETIN SUPERCEDES LM100-006. THE CHANGES FROM THE ORIGINAL BULLETIN ARE HIGHLIGHTED WITH A GRAY BACKGROUND AND ASTERISKS.
SECTION: 100-04
Drone Noise on Supercharged Vehicles with 20-inch Wheels
AFFECTED VEHICLE RANGE:
New Range Rover (LM) VIN: 6A198058 onwards Supercharged V8 with 20-inch wheels only
CONDITION SUMMARY:
DRONE NOISE ON SUPERCHARGED VEHICLES WITH 20-INCH WHEELS
NOTE:
The drone noise will not be evident on all vehicles.
Situation:
A customer may report a concern of a droning noise in the cabin when reaching speeds between 55-75 mph (88-120 kph). The noise will remain constant until the vehicle speed is significantly reduced. The drone noise is caused by a vibration which resonates at a particular frequency. The drone noise could be described as similar to the sound created when blowing over the top of an empty glass bottle. Road surface, vehicle speed and ambient temperature are cumulative factors that could cause the resonant sound.
The suspension setting for the supercharged V8 transmits a resonant frequency from the 20-inch wheel/tire assembly to the vehicle body. This resonant frequency coincides with the natural frequency of the body cabin, resulting in the audible drone.
Action:
On a customer concern basis only and verification of the drone noise specified, refer to the Repair Procedure detailed in this bulletin to replace the shock absorber mass damper.
PARTS
WARRANTY:
NOTE:
Repair procedures are under constant review, and therefore times are subject to change; those quoted here must be taken as guidance only. Always refer to DDW to obtain the latest repair time. DDW requires the use of causal part numbers.
Labor only claims must show the causal part number with a quantity of zero.
REPAIR PROCEDURE
INSTALL NEW MASS DAMPER
1. Open the hood.
2. Release the hood gas struts and secure in the access position.
3. Remove the plastic covers from the top of each of the front suspension shock mounts.
4. If the removed cover is of a two-piece design, discard the upper section and retain the lower section for re-installation.
5. If the removed cover is of a one-piece design, discard the existing cover.
6. Mark the insulator and lower cup positions relative to the body. (Figure 2)
CAUTION:
The lower cup should not rotate when removing the mass damper. All residual thread locking material must be removed from the cup threads.
7. Using an air powered impact wrench, release the mass damper from the lower cup.
NOTE:
Global Technical Reference (GTR) lookup sequence is as follows:
GTR Home> NAS > Service Information/LM - New Range Rover/2006 > Workshop Manuals - New Systems> Bookmark "Chassis/Suspension/204-01: Front Suspension" Link "Shock Absorber and Spring Assembly (60.30.25/99)"
8. If either of the following conditions exist, the complete strut assembly should be replaced in accordance to New Range Rover Workshop Manual Section 204-01 Shock Absorber and Spring Assembly operation 60.30.25/99:
^ If the lower cup rotates when removing the mass damper.
^ If unable to remove the residual thread lock agent from the lower cup using a wire brush.
9. Verify that the shock absorber securing nuts are tightened to 85 Nm (63 lbf-ft).
10. Install the lower half of the shock absorber plastic cover to the body opening on the shock mount as follows:
^ If the existing plastic cover previously removed from the shock mount was of a two-piece design, install the lower section of that existing shock absorber cover to the body opening.
^ If the existing plastic cover previously removed from the shock mount was of a one-piece design, install the lower section of a new shock absorber cover (RBD500011) to the body opening.
11. Apply a 5 mm (0.2 in) bead of suitable thread lock fluid (e.g. Loctite 648) to the threads of the new mass damper.
12. Install the new mass damper to the shock absorber lower cup and tighten by hand.
NOTE:
The lower cup should not rotate when tightening the mass damper.
13. Tighten the nut of the new mass damper to *20 Nm (15 lbf-ft)*, ensuring that the shock absorber cup does not move when tightening.
CAUTION:
Failure to prevent the damper rod/top mount from turning may result in the plastic location lug shearing.
14. Insert an 8 mm (5/16 in) Allen key through the center of the mass damper into the hex of the damper rod to prevent the damper rod/top mount from turning.
15. Using an open-ended or ring-ended torque wrench, tighten the mass damper to 20 Nm (15 lbf-ft), ensuring the damper rod does not turn.
NOTE:
Shown above are illustrations of the under-hood liner are at 50% of full-scale. A full-scale template may be created to assist in marking the square and the four points of the "X" that will be cut.
16. Measure and mark the four points of an "X" onto the under-hood liner, as dimensioned in Attachments 1 and 2, as follows: (Illustrated in Figure 3)
17. Release the liner from the hood for access.
18. Cut through the hood liner diagonally across the square, notching out the lower triangle piece as illustrated in Figure 3.
19. Discard the lower triangle piece.
20. Keeping the outer liner material intact, carefully separate and remove the backing foam from the liner in the areas behind the three remaining triangles only.
21. Fold the liner material of three triangles back and under the liner, leaving a neat and straight edge.
CAUTION:
When using aerosol spray adhesive, care must be taken to protect the surrounding work area from over-spray.
NOTE:
Sufficient time is needed for the contact adhesive to cure. Closing the hood will allow the liner to hold the correct position until the adhesive has hardened. The hood should remain closed for a minimum of 24 hours.
22. Using a suitable contact adhesive (e.g. STC50550), secure the folded back triangles to the hood and to the rearmost edges of the liner.
23. Once the adhesive has hardened, properly secure the under-hood liner and gas struts.
24. Ensure the tires are set to the correct inflation pressures before returning the vehicle.
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