Shake/Vibration in Steering Wheel, Floor, Seat at Highway Speeds on Smooth Roads (Diagnose/Balance Tires/Wheels)

This bulletin is being revised to add the 2005 model year, add additional diagnostic information, and include the Coats XR1850. Please discard Corporate Bulletin Number 00-03-10-007F (Section 03 - Suspension).

Some customers may comment on shaking/vibration in the steering wheel, floor or seat while driving at highway speeds (typically between 60-72 mph (96-115 km/h)) on smooth roads.

These specific vehicles may be sensitive to various rotating mass assemblies, especially if they are considered to be out-of-balance.

1. Visually inspect the tires and the wheels. Inspect for evidence of the following conditions and correct as necessary:

•	Missing balance weights

•	Bent rim flange

•	Irregular tire wear

•	Incomplete bead seating

•	Tire irregularities

•	Mud/ice build-up in wheel

•	Stones in the tire tread

2. Set the tire pressure to 30 psi (205 kPa) COLD.
3. Road test the vehicle with the Electronic Vibration Analyzer (EVA) essential tool for a sufficient distance on a known, smooth road surface to duplicate the condition. Record the Hertz (Hz) reading as displayed by the EVA onto the tire data worksheet found at the end of this bulletin. This should be done after a tire break-in period of at least 10 miles (16 km) at 45 mph (72 km/h) or greater, in order to eliminate any possible tire flat-spotting.
4. If the road test indicates a shake/vibration still exists, check the imbalance of each tire/wheel assembly on a known, calibrated, off-car dynamic balancer. If any assembly calls for more than ¼ ounce on either rim flange, remove all balance weights and rebalance to as close to zero as possible.

Important: Some GM dealers may have a Hunter GSP9700 Road Force Balancer, or a Coats XR1850 Runout Balancer. Either will simplify Step 5 by not requiring dial indicators. If a Hunter GSP9700 machine is available, it may also be used to measure the radial force of the tire/wheel assembly. A guideline here is 18 lbs or less.

5. While on the balancer, measure wheel runout. If radial or lateral runout exceeds .020 in (0.50 mm) for aluminum wheels (.030 in (0.76 mm) for steel wheels), replace the wheel.
6. After confirming wheel balance and wheel runout, if any changes were made, road test the vehicle again.
7. If the smooth road shake/vibration still exists:

Important: The completed worksheet must be attached to the hard copy of the repair order.

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If a Hunter GSP9700 Road Force/Balancing machine is used, record radial force variation (RFV) on the worksheet at the end of this bulletin. If one or more of the tire/wheel assemblies read more than 18 lbs, match mount the tire to the wheel to get below 18 lbs. Readings of 12 lbs or less are preferable for sensitive customers.

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If a Coats XR1850 Runout/Balancing Machine is used, record radial runout of the tire/wheel assemblies on the worksheet at the end of this bulletin. If one or more of the tire/wheel assemblies are more than .040, match mount the tire to the wheel to get below .040. Readings of .030 inch or less are preferable for sensitive customers.

•	If the RFV or runout cannot be reduced to an acceptable level, replace the affected tire(s) under the guidelines of the GM Tire Warranty.

•	The screened tire program is only available for the General branded tires used on the Buick LeSabre. Complete the tire request form at the end of this bulletin and fax to Continental/General.

•	Road test the vehicle to ensure the shake/vibration has been eliminated.

Important: THE CONTROL ARMS SHOULD ONLY BE INSTALLED ON VEHICLES IF, AFTER THE TIRE AND WHEEL DIAGNOSIS AND REPAIRS HAVE BEEN PERFORMED, THE VIBRATION CONDITION STILL EXISTS.

8. Replace both lower control arms on vehicles built prior to the following VIN breakpoints. On Aurora, Bonneville, DeVille, Park Avenue, Park Avenue Ultra and Seville models, a newly developed hydro-bushing lower control arm with improved damping characteristics has been released. This control arm is not used on the LeSabre. The new lower control arms may provide an incremental improvement to the vehicle ride. Customers who have become "tuned in" to the shake condition may still feel some shake in the vehicle after the new lower control arms are installed. Refer to Lower Control Arm Replacement in SI (refer to the Parts Information table below for SI document ID numbers).

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use: