A/T Controls - Drone/Boom/Vibration At 1000-1300 RPM
TECHNICALBulletin No.: 08-07-30-044D
Date: November 18, 2009
Subject: Phasing Drone, Boom, Moan or Vibration in Seat, Floor Pan or Door panel at 87-97 kph (54-60 mph) or at 64 kph (40 mph) in 6th gear or 1000-1300 RPM with Torque Converter Clutch (TCC) Engaged (Reprogram TCM and Install Washers [On Vehicles Built Without
Washers] )
Models:
2008-2010 Cadillac CTS
with 6L50 Automatic Transmission (RPO MYB)
Supercede:
This bulletin is being revised to add the 2010 model year and include re-indexing of the propshaft. Please discard Corporate Bulletin Number 08-07-30-044C (Section 07 - Transmission).
Condition
Some customers may comment on a drone, boom, moan or vibration in the seat, floor pan or door panel during light acceleration which phases in and out in intensity.
The condition may be most noticeable at about 87-97 kph (54-60 mph) or about 40 mph in 6th gear at 1000-1300 engine RPM with the torque converter clutch (TCC) engaged and occurs over a speed range of 5 to 8 km/h (3 to 5 mph).
Cause
This condition may be caused by the following:
- Driveline imbalance vibration through the rear cradle mount and into the body, or
- The rear axle assembly responds to engine firing frequencies passed through the driveline when the torque converter clutch (TCC) is engaged.
Correction
For 2008-2009 Vehicles - Calibration Update
This condition can be verified by driving the vehicle to duplicate the concern and using the Tech 2(R) to turn off the TCC. If the noise stops when the TCC is turned off, the calibration detailed below should help to eliminate the noise or vibration.
Important
- This calibration may result in decreased fuel economy up to approximately one mpg/kpg. Because of this, the software should not be used in a vehicle without this concern.
- For 2008 vehicles, there are two calibration part numbers that are "selectable" for this controller. Read the description to determine the correct calibration for this condition.
- DO NOT replace rear drive axle or propshaft for this concern.
A revised calibration has been developed to correct this condition. Technicians are to reprogram the transmission control module (TCM) using SPS with the latest software available on TIS2WEB. Refer to the Service Programming System (SPS) procedures in SI. As always make sure your Tech 2(R) is updated with the latest software version.
For Vehicles Built Prior to VIN Breakpoint 90159377 - Install Insulator Washers Between the Rear Drive Axle and the Rear Cradle After Reprogramming
1. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in SI.
2. Place a transmission jack stand under the rear differential assembly.
3. Remove the two front differential mounting bolts
4. Install the rubber insulators (2), GM P/N 20827776, between the rear drive axle and the body at the front differential bolt locations.
5. Install the two front differential mounting bolts.
Tighten
Tighten the front differential mounting bolts (1) to 175Nm (129 lb ft).
For Vehicles Built Prior to VIN Breakpoint 90158774 - Install Washers Between the Rear Cradle Mount and Lower Rate Plate
1. Install a support fixture to support the rear frame assembly.
2. Remove the frame to body mounting bolts one at a time in the order shown above (1, 2, 3, 4). Install one washer, GM P/N 1646989, in the following location on the bolt (1).
3. Reinstall the bolts.
Tighten
- Tighten the cradle to body bolt rear body mount to 100 Nm plus 80-95 degree torque angle.
- Tighten the cradle to body bolt front body mount to 200 Nm plus 60-75 degree torque angle.
When repairs are complete, any additional disturbance may be related to Corporate Bulletin Number 08-06-05-001 - Noise/Moan/Drone/Resonance/Vibration at Idle While in Drive with Foot on Brake. Please review its contents and perform the necessary adjustments.
For All Vehicles - Re-Index the Propshaft
1. Inspect the alignment of the yellow and orange paint dots on the propeller shaft and the drive flange. Make sure they are aligned.
2. If the paint dots are aligned and the problem persists, rotate propshaft. The two parts can be mated together in three positions. If the matched position does not work. Unbolt the propshaft with transmission in neutral, rotate one position and re-bolt. Re-evaluate in that position. If not acceptable, unbolt prop with trans in neutral again, rotate once more in the same direction to evaluate the third position. Drive the vehicle to verify that the condition is resolved.
Parts Information
Warranty Information
For vehicles repaired under warranty, use the table above.
Disclaimer