CTS RWD V8-6.2L SC (2009)
Control Arm: All Technical Service Bulletins
Steering/Suspension - Interior Highway Speed Vibration
TECHNICAL
Bulletin No.: 09-00-91-001A
Date: March 15, 2010
Subject: Shake/Vibration in Steering Wheel at Highway Speeds on Smooth Roads (Diagnose/Balance Tires/Wheels)
Models:
2008-2009 Cadillac CTS Sedan (RWD Only)
Excludes CTS-V, CTS-4 (AWD) Models
Supercede:
This bulletin is being revised to simplify the diagnostic requirements in the attached worksheet and refine the diagnostic procedure to target vibrations
specifically felt through the steering wheel. Please discard Corporate Bulletin Number 09-00-91-001 (Section 00 - General Information).
Condition
Some customers may comment on shaking/vibration in the steering wheel while driving at highway speeds (typically between 65-75 mph (105-121 km/h)
on smooth roads.
Correction
Use the following information to diagnose and correct the concern.
Notice
Do NOT align the vehicle or replace shocks for this condition. Adjusting wheel alignment or shock replacement will NOT correct a smooth road shake
condition.
1. Road test the vehicle using the Electronic Vibration Analyzer (EVA) essential tool. Drive for a sufficient distance on a known, smooth road
surface to duplicate the condition. Determine if the vehicle is sensitive to brake apply. If the brakes are applied lightly and the pulsation felt in the
steering wheel increases, refer to the Brakes section of the service manual that deals with brake-induced pulsation.
If you can start to hear the vibration as a low boom noise (in addition to feeling it), but cannot see it, it likely has a first order (one pulse per
propshaft revolution) driveline vibration. Driveline first order vibrations are high enough in frequency that most humans can start to hear them at
highway speeds, but are too high to be able to be easily seen. These issues can be caused by driveline imbalance or misalignment. If the vehicle
exhibits this low boom and the booming pulses in-and-out on a regular basis (like a throbbing), chances are good that the vehicle could have
driveline vibration. This type of vibration is normally felt more in the "seat of the pants" than the steering wheel. There is a separate analysis for
driveline vibrations. If this is the situation, refer to Corporate Bulletin Number 08-07-30-044D.
2. Next, 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 16 km (10 mi) at 72 km/h (45 mph) or greater, in order to eliminate any possible tire flat-spotting. This
reading confirms what the vehicle vibration frequency is prior to vehicle service and documents the amount of improvement occurring as the result
of the various steps taken to repair. Completing the Steering Wheel Shake Worksheet below is required. A copy of the completed worksheet
must be saved with the R.O. and a copy included with any parts returned to the Warranty Parts Center for analysis. A reading of 35 to 50
Hz indicates a first order propshaft vibration. If this is the situation, refer to Corporate Bulletin Number 08-07-30-044D. Generally, a reading of
less than 20 Hz indicates a tire/wheel vibration and if this is the reading obtained, continue using this bulletin.
3. Visually inspect the tires and the wheels. Inspect for evidence of the following conditions and correct as necessary:
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Missing balance weights
-
Bent rim flange
-
Irregular tire wear
-
Incomplete bead seating
-
Tire irregularities (including pressure settings)
-
Mud/ice build-up in wheel
-
Stones in the tire tread
-
Remove any aftermarket wheels and/or tires and restore vehicle to original condition prior to diagnosing a smooth road shake condition.
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Ensure the wheels are centered on the hub by loosening all wheel nuts and hand-tightening all nuts first by hand while shaking the wheel, then
torque to specifications using a torque wrench, NOT a torque stick.
4. If corrections to any items in Step 3 were made, road test the vehicle to determine if the vehicle still exhibits the smooth road shake conditions.
If the smooth road shake/vibration still exists, continue below to diagnose wheel and tire concerns.
