Frankie2blue

I have been noticing a rubbing like sound coming from the rear end area on my car when it's cold and rolling. It's a rubbing or scraping like sound when moving definitely coming from the rear. Probably the axels or transmission area. Now if I put in the clutch and let it roll to a stop, it's still there. Shut off the motor and roll to a stop and its still there. Once the car heats up, it dissipates. Any ideas what this thing could be?

eroc022

Bulletin No.: 09-04-20-001C

Date: September 17, 2012

Subject: Front Tire Chatter/Noise vs. Rear Differential Chatter
Models:
2006-2013 Chevrolet Corvette

Supercede:
This bulletin is being revised to add the 2013 model year. Please discard Corporate Bulletin Number 09-04-20-001B (Section 04 - Driveline/Axle).

The purpose of this bulletin is to address a chatter noise during low speed tight turn conditions (i.e. parking lot, driveway, etc.) primarily during cooler ambient temperatures. The condition can be experienced in all directions: right, left, forward, reverse. The condition typically reduces or diminishes when the vehicle warms up, but may be worse when the pavement is wet.
Note
For the 2011-2013 model year, the Goodyear F1 tire, available on Corvette Grand Sports and Z06 models, has a significant tread design change. This new design is more susceptible to tire chatter or hop than the previous design.

This condition may be caused by two potential sources of chatter:
- Front tire hop

- Rear differential chatter/noise

The following subjective evaluation will help identify the correct source of the suspect noise.

Evaluation

Test Conditions/Location
- Vehicle condition: Condition typically occurs following an extensive ambient soak of the vehicle. A vehicle soak of at least eight hours during cool outside ambient temperatures is required prior to evaluation.

- Road surface: Clean (e.g. limited gravel), dry asphalt or concrete surface with sufficient space to complete two to three full vehicle turns at first gear idle speed.

Important
Limit the evaluation to four full vehicle circles.

1. With the engine running and the vehicle at rest, turn the steering wheel in the direction of the intended turns until full steering lock is achieved. Allow the steering wheel to come off of full lock position slightly to prevent power steering system damage.A hand position at the bottom of the steering wheel (6 o'clock) assists in the evaluation, but is not required.

2. Engage the clutch in first gear (manual transmission) or release the brake and place the shifter in Drive (automatic transmission). The objectionable noise should be quickly detected once the vehicle has made one to two circles.

3. With the vehicle moving in a tight circle and the objectionable noise present, move the steering wheel in 1/4 turn increments away from the full lock position. A maximum of 1/2 to 3/4 turn from full lock should be sufficient to determine the source.

4. With a hand at the 6 o'clock position as a reference indicating full lock, move the steering wheel to the 3 or 9 o'clock position and hold briefly to evaluate (two to three seconds). Continue turning from the 3 or 9 o'clock position to the 12 o'clock position and re-evaluate (two to three seconds). Repeat if necessary for a maximum of four complete vehicle circles.

For more information evaluating this condition, U.S. dealers should refer to the May 2010 Emerging Issues, Course Number 10210.05 - What's Hot: Cars: Corvette Vibration and Noise During Parking Lot Maneuvers (available at www.gmtraining.com). Dealers in Canada should refer to the June 2010 TAC TALK - Video on Demand (VOD).

Diagnosis
- Front Tire Hop: The objectionable noise will reduce in severity or cease during the turning sequence immediately when the steering wheel is turned (1/4 steering turn will typically dramatically reduce front tire chatter). In colder ambient temperatures (<-18°C (20°F)), an additional 1/4 turn (total of 3/4 turn) may be necessary to sufficiently eliminate the front tire noise.If the diagnosis indicates the issue is tire hop, the condition is within the design criteria (normal condition) of the vehicle.

Important
DO NOT attempt repairs or change the differential fluid.

Inform the customer the noise is tire hop and is caused by the large amount of tire scrubbing across the pavement as the vehicle is turned.
- Rear Differential Chatter/Noise: At the 1/4 and 1/2 turn stops the objectionable noise WILL NOT reduce in severity (e.g. loud, volume) but may reduce in frequency (e.g. time between chatter events).If the diagnosis indicates the differential is the source of the noise, follow the instructions below:

Important
DO NOT add a friction modifier in combination with DEXRON(R) LS fluid. The limited slip and active handling features may be adversely affected.

- 2005-2008 Models: Refer to Corporate Bulletin Number 07-04-20-002B. The service bulletin specifies to drain and fill, only with DEXRON(R) LS for customer concerns of rear differential chatter. Note: fluid used prior to DEXRON(R) LS is a synthetic 75W90 requiring 4-6 oz of friction modifier. DEXRON(R) LS contains friction modifier which does not require an additional additive.

- 2009 and later Models: At the start of production for the 2009 model year, DEXRON(R) LS rear axle fluid was implemented to address rear differential chatter. Refer to Symptoms - Rear Drive Axle in SI for further diagnosis.

Frankie2blue

Thanks for the bulletin, but my noise is not really involved with any turning of the vehicle. It is happening when cold and simply rolling in a straight line. Almost sounds as if the tire could be rubbing on something ( which I doubt) but its that kind of noise and not a chatter or vibration. Happens even if I put the tranny in neutral and roll. I tend to suspect something in the transaxle or something like that, but I'm not sure what.

eroc022

What year is your car? How is it normally driven? Mileage? Tires rubbing I dont think would squeak, like I am thinking....wheel bearing is a possibility....

Frankie2blue

Car is a 2008 and it has 6100 miles on it. As I said the noise is more like a grating or rubbing sound. This car is pampered and always has been. It is not real loud but it is there. when it warms up, its gone. Almost like the sound you would get if you wore brake pads down to nothing and hear that metal to metal type of sound.

capevettes

My low mileage 06 was doing the same thing when cold. I changed out the rear end fluid (follow the DIY tutorial). Problem solved

Mike's LS3

Could it be the parking brake shoe (not brake pads) adjusted to tight and dragging to the point it's worn out? Also check rear brakes for a bad piston not releasing and dragging one of the brake pads.

DONZI TOM

I have a 08 Z06 and it makes the same noise only for about the first mile of driving. It is more noticable when decelerating. Mine also will do it with the transmission in neutral clutch out and rev to about 2500 rpm. Once it warms up you can drive all day and never hear the noise again. Let me know if your does it in neutral also.

dmuellenberg

The OP said it also does it with the clutch in, so that would be the same as having the shifter in neutral (transmission is disengaged). I would also check the axle nuts to be sure they are tight (not sure why it would only make noise when it's cold but I would still check them).

smitty1966

My 06 Z51 did this, worse in reverse. Had the shop change rear end fluid and add posi trac additive and it went away. Sold it years later with 80000 miles on it and no problems or noise.

peterpiper

how often do you drive? Rusty rotors? -pp

Mr. Gizmo

OP should change rear end differential fluid and add the positrac additive.

That would be the first thing I would do and the least costly, before he goes running down other mechanical paths.