steel_3d

Sorry to revive a slightly old thread, but I thought I'd keep it alive a bit and see if there's any quiet Vettes out there at all.

I agree with i_york that there's not supposed to be this much gear lash, and I haven't seen this on other cars.

One easy way to duplicate the noise that I found yesterday is to jack up the car, grab one of the wheels (or hubs, if the wheel is off) and lightly turn it one way and the other. There's quite a lot of play, some play I've seen in other cars, but the clunk if much louder. It sounds like it's coming from inside the tranny when I'm under the car, not just the diff. It's quite loud.

The other reason I believe a lot of it comes from inside the tranny, is that just pressing and releasing the clutch in neutral at a standstill causes a lash type noise (while not as loud as with a gear enaged).

It seems to me that there's no simple fix for this, like just resetting the lash in the diff The whole tranny feels loose. Why? Why can't Tremec/GM set lash properly? In response to lil red corvette, there's a reason why there's a concept called setting gear lash, part of it is to eliminate noises of this sort. If you had proper gear lash of a few thousandths of an inch everywhere, the oil would cushion the gears and you wouldn't hear athing. The other reason is to reduce impact forces on gears. I'm surprised we don't hear of various gears shattering in Vettes. I know for a fact that me driving on the road course, on and off the throttle near redline, hard shifts near redline, is a little more wear and tear than doing that in stop and go traffic, mr lil red corvette, and that's what these cars are supposedly made for. I'm frankly surprised they live through it. I've rebuilt trannies, set gear lash on diffs and awd transer cases, it's not that hard, maybe they're just cutting costs? Or it's part of their procedures but the monkey doing the work decides not to do it?

I've heard about the driveline clunk in many magazine/online/tv reviews of the Vette, which also suggests that most cars don't do this. The question is, are there ANY Vettes that don't do this?

I also tightened and loctited my axle nut today that was way loose, I could easily shake the cv joint in the hub. My front sway bar end links are also shot on a brand new car after 13k miles, adding to the various clunking noises. Not to mention the creaky roof. I wish GM read threads like this and paid attention... There's no reason a car in this price range should ever exhibit these kinds of issues, much less right off the lot or after 10k miles. Other than this I love my ****in car!

User 2623

Steel_3D I always suspected this was a transimission issue. So thanks for your input on this subject. I went to the dealer again just last week about this issue and they are saying this drivetrain lash is acceptable and normal for the car. I did not have this with the C5. Unfortunately [and a bit fustrating] I can't seem to get the car to consistently [really] hard clunk as I experience when in stop-n-go traffic.

I will use the example you provided for duplicating the issue and see if the tech's @ B'walk chevy in Redwood City, CA can do anything. They are the best service I have come across, but will not do anything unless the problem is significantly duplicated and repilicable.

By the way for the creaky roof try this fix.. seems to work.
http://forums.corvetteforum.com/show....php?t=1956846

tka

Hi guys, I think I have exactly the same problem (M6 2005). I'm pretty sure that I didn't hear this clunk sound 6 months ago but now I hear it every time when I'm changing gears in slow speed.
I'm gonna schedule service appointment tomorrow. I also need to replace my clutch return spring as it broke down.
Do you have any advice what I should say/show/do when I drop my car to dealer for service? Is there some TSB which I should refer or what?

Fortunately it is still under warranty, so hopefully they will fix something.

Bobz08C6

For what it's worth I have the same klunk. load/unload, light acceleration, very slow speed, straight line, 1st or 2nd in an 08 Coupe, A6, Z51 with 500 miles. Only occurs when the car is fully warmed up.

JPchevy

I am wondering if you had this taken care of yet. The clunk can be the wheel driveshaft nuts. The original nuts not holding their torque, allowing the play causing the clunk at low speeds (and yes, when turning also).

There is also a bulletin from GM regarding a "snap clunk noise" when turning that can be associated with the stabilizer links:

"Condition/Concern:
Some customers may comment of a snap clunk noise from under the vehicle. This may occur while driving or parking lot maneuvers. This may be the result of the stabilizer links making noise.

Recommendation/Instructions:
Isolate the front and rear stabilizer bar links one at a time and evaluate. Replace any link subject to noise.

Note: The XLR base vehicle is equipped with a front stabilizer only. XLR V-series and the Chevrolet Corvette have front and rear stabilizers.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed."

The wheel driveshaft nut bulletin: ##07-04-95-001: Tapping or Scraping Noise From Rear Wheel Area (Replace Wheel Drive Shaft Nut)

I know it says tapping or scaping, but this TSB has also cured the problem as well.

Best of luck

ADIBELC6

#PIC4475A: Snap Clunk Noise From Front Or Rear Of Vehicle - keywords click link noise snap stabilizer stable suspension - (Mar 6, 2008)


Subject: Snap Clunk Noise From Front or Rear Of Vehicle


Models: 2004-2008 Cadillac XLR and V- Series

2005-2008 Chevrolet Corvette




--------------------------------------------------------------------------------

This PI was superseded to update model years. Please discard PIC4475.


--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Some customers may comment of a snap clunk noise from under the vehicle. This may occur while driving or parking lot maneuvers. This may be the result of the stabilizer links making noise.

Recommendation/Instructions:
Isolate the front and rear stabilizer bar links one at a time and evaluate. Replace any link subject to noise.

Note: The XLR base vehicle is equipped with a front stabilizer only. XLR V-series and the Chevrolet Corvette have front and rear stabilizers.

ADIBELC6

PIP3896: Clunk Noise When Shifting More Noticeable At Low Speeds - keywords clutch manual throttle transmission - (Aug 28, 2007)


Subject: Clunk Noise When Shifting More Noticeable at Low Speeds


Models: 2004-2007 Cadillac CTS-V

1997-2007 Chevrolet Corvette

2005-2006 Chevrolet SSR

2004-2006 Pontiac GTO

Equipped with a Tremec 6-speed Manual Transmission




--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
While driving in a steady slow speed parade type situation a clunk-clunk noise from the driveline may be heard when depressing and releasing the clutch pedal, between shifts or quickly depressing and releasing the throttle.

Recommendation/Instructions:
The noise is a normal torque reversal in the driveline and a combination of axle backlash, front and rear drive shaft rubber isolation flanges, drive shaft center support, and a dual mass flywheel all working together. This is a normal characteristic and not a condition of operation concern. No repairs should be attempted.

Also reference the latest version of TSB 03-07-29-004 for further manual transmission operating characteristics.

User 2623

Would this apply also to an automatic transmission?

steel_3d

I assume so. It basically says "our **** is sloppy, and we're not gonna do anything about it". Auto is only slightly different with a mushier torque converter in the middle...

PharmZ

Does anyone know what SIZE the wheel drive shaft nut is? I'm pretty sure I don't have the proper socket in my toolkit!

Zig

have you confirmed your fluid levels? both trans, diff. and clutch (if a manual trans.)

pwoolford

I had this issue on mine and it turned out to be something cracked on the passenger side half-shaft. I was under warranty and the dealer replaced the half-shaft.

steel_3d

The axle nut is about 34mm, 35mm works as well, or a standard size around that (1-3/8").

PharmZ

Thanks, steel_3d! I haven't been able to find one yet, but I'll hit the auto parts stores tomorrow. One of my fellow HPDE attendees checked the axle nuts right before my first run and I was EXTREMELY glad he did.

COL Dave L

TSB #07-04-2-002A Subject: Rear Axle Clunk and/or Chatter Type Noise on Turns., dated 01-09-2008. A newly developed fluid from GM is to be used in place of the old fluid which also used anti-slip additive. Tell the dealer and it's covered under warranty.

Dave
06/C6/A6/Z51

glenB

Bulletin No.: 03-07-29-004D

Date: October 17, 2007

INFORMATION

Subject:
Manual Transmission Operating Characteristics

Models:
2008 and Prior Passenger Cars and Light Duty Trucks (Including Saturn)
2008 and Prior Chevrolet and GMC Medium Duty Trucks
2006-2008 HUMMER H3
2008 and Prior Isuzu Medium Duty Trucks

with Manual Transmission

Supercede:

This bulletin is being revised to add the 2008 model year. Please discard Corporate Bulletin Number 03-07-29-004C (Section 07 - Transmission/Transaxle).

Even though this bulletin attempts to cover operating characteristics of manual transmissions, it cannot be all inclusive. Be sure to compare any questionable concerns to a similar vehicle and if possible, with similar mileage. Even though many of the conditions are described as characteristics and may not be durability issues, GM may attempt to improve specific issues for customer satisfaction.

The purpose of this bulletin is to assist in identifying characteristics of manual transmissions that repair attempts will not change. The following are explanations and examples of conditions that will generally occur in all manual transmissions. All noises will vary between transmissions due to build variation, type of transmission (usually the more heavy duty, the more noise), type of flywheel and clutch, level of insulation, etc.

Basic Information

Many transmission noises are created by the firing pulses of the engine. Each firing pulse creates a sudden change in angular acceleration at the crankshaft.

These changes in speed can be reduced with clutch damper springs and dual mass flywheels. However, some speed variation will make it through to the transmission. This can create noise as the various gears will accel and decel against each other because of required clearances.

Gear Rattle

Rattling or grinding (not to be confused with a missed shift type of grinding, also described as a combustion knock type of noise) type noises usually occur while operating the engine at low RPMs (lugging the engine). This can occur while accelerating from a stop (for example, a Corvette) or while operating at low RPMs while under a load (for example, Kodiak in a lower gear and at low engine speed). Vehicles equipped with a dual-mass flywheel (for example, a 3500 HD Sierra with the 6-speed manual and Duramax(R)) will have reduced noise levels as compared to vehicles without (for example, a 4500 Kodiak with the 6-speed manual and Duramax(R)). However, dual-mass flywheels do not eliminate all noise.

Neutral Rattle

There are often concerns of rattle while idling in neutral with the clutch engaged. This is related to the changes in angular acceleration described earlier. This is a light rattle, and once again, vehicles with dual mass flywheels will have reduced noise. If the engine is shut off while idling in neutral with the clutch engaged, the sudden stop of the engine will create a rapid change in angular acceleration that even dual mass flywheels can not compensate. Because of the mass of all the components, this will create a noise. This type of noise should not be heard if the clutch is released (pedal pushed to the floor).

Backlash

Backlash noise is created when changing engine or driveline loading. This can occur when accelerating from a stop, coming to a stop, or applying and releasing the throttle (loading and unloading the driveline). This will vary based on vehicle type, build variations, driver input, vehicle loading, etc. and is created from the necessary clearance between all of the mating gears in the transmission, axle(s) and transfer case (if equipped).

Shift Effort

Shift effort will vary among different style transmissions and synchronizer designs. Usually the more heavy duty the transmission, the higher the shift effort because of the increased mass of the components. Shift effort can also be higher in cold weather because the fluid will be thicker. Medium duty transmissions will not shift as quickly as a Corvette transmission. To reduce shift effort, do not attempt to rush the shift - allow the synchronizers to work as designed. Shifting harder will only increase the chance of rushing past the synchronizer leading to grinding while shifting.

Non-Synchronized Gears

Some light duty truck transmissions in 1st gear (creeper-gear) and reverse gears in various transmissions, along with all gears in some medium duty transmissions, may be non-synchronized. This means there is not a mechanism to match input and output shaft speeds to allow for a smooth shift. This function is left up to the driver. This can be noticed if a shift into 1st or reverse is attempted while the vehicle is rolling or before the input shaft stops rotating leading to a gear grind. The grinding can be reduced by coming to a complete stop and pausing for a moment before shifting into the 1st or reverse gear. Some slight grinding can be expected. In medium duty non-synchronized transmissions, the driver must match input shaft (engine) speed to output shaft (driveshaft) speed with every shift. This can be accomplished by double clutching, or by using other methods. If the driver is not able to perform this function properly, there will be gear grinding with each improperly completed shift. Driver training may be required to correct this condition. Clutch brakes are used in medium duty non-synchronized transmissions to allow a shift into gear at a stop. The clutch brake is used to stop the input shaft from spinning, allowing a shift into gear at a stop without grinding. The clutch brake is activated by pressing the clutch pedal all the way to the floor. When the clutch brake is used, it is possible to have a blocked shift with the vehicle stationary. If this occurs, engage the clutch slightly to rotate the input gear to allow the shift. The clutch brake is intended to only be used while at a stop. Care must be taken to not activate the clutch brake while shifting between gears. This could lead to excessive grinding or a blocked or missed shift.

Skip Shift

Currently, the Cadillac CTS-V, GTO, and Corvette (other models may follow) equipped with the 6-speed manual transmission have a feature referred to as a skip-shift. This feature only allows a shift from 1st to 4th gear when the indicator lamp is illuminated on the dash. Dealers cannot disable this feature as it was established to help meet fuel economy standards. The conditions for this feature are: engine coolant at normal operating temperature, vehicle speed of 24-31 km/h (15-19 mph), 21% or less throttle being used (refer to Service Information or the Owner Manual for more details.)

User 2623

Is there a TSB/ Fix for this particular Backlash? As in "GM may attempt to improve specific issues for customer satisfaction". This Bulleting describes the issue but does not give a course of action in re: Backlash. Is there more?

glenB

That's it, sorry

tka

My clunk sound came also from axle nut. They replaced both of them in dealer and that fix the problem.
BUT when I was washing my car today I noticed huge scratches on the passenger side rear wheel. Scratches are definetely made by some tool, since they are exactly straight and there are two scratch parallel.
I will call them tomorrow and say that I want a new wheel.

SnowyATX

I have the same issue as well and mine is an '08.