My car has developed a noise which seems to emanate from the gearbox. It is a 'whirring' sound which is proportional in frequency to the gear the car is in and the road speed.

o the noise only occurs when the car is in gear.

o the noise occurs regardless of whether the clutch is engaged or disengaged

o the noise is proportional to road speed, not engine speed

The best way to exhibit the problem is to get the car coasting at a constant speed. With the clutch depressed (and the engine quiet and idling at low rpms), the noise is very pronounced. I can row through various gears, and the frequency of the whirring noise is different in each gear, highest pitch in low gears. If I move the shift lever from a gear position to neutral, the whirring noise trails off and stops after a few seconds.

Any ideas appreciated.

thanks,

-ag

 

I recently noticed this also. 2004 Z06....about 4k miles on the clock. I don't think I notice it as much as yours. Any ideas anyone....throwout bearing ???

 

Sounds like something in the layshaft, likely a bearing. If the noise has a different frequency in each gear, then it has to be in the layshaft system. Since the layshaft is turning when the car is in gear, even with the clutch depressed, the speed of the layshaft is the only thing that is changing. Try to note if it gets quiet in any one gear. If the problem is associated with one of the bearings in the gears, it will be quiet in one gear. If it happens in EVERY gear, then it is more likely one of the main layshaft bearings.

How many miles and are you still in warranty?

 

Thanks. The car has 30k miles on it and is still under (extended manufacturer) warranty.

One thing which might be relevant. I had the rering done under warranty about a year ago. In the process of removing the engine to do the work, the dealer broke the transmission bell housing. They admitted this and replaced while doing the valve ring work. Quite some time elapsed between this incident (~1 year ago) and the development of the transmission noise (started about a month or so ago).

-ag

 

I started noticing this exact same thing in my 04 about a week ago at around 12K miles.

 

I took the car to the dealer. This was, unfortunately, a waste of time.

Both the service manager and the technician went for test drives and can hear the noise. However, they claim it is not loud enough to distinguish the source.

They want me to bring it back when it gets worse. Extended warranty expires in a year, so it won't be more than six months from now that I'm back, regardless of whether it is worse.

Any way to distinguish whether this is a problem with torque tube bearings v. thrust bearings v. layshaft without major work disassembling the transmission?

thanks,

-ag

 

you just got to love those dealers. Their service departments are not capable of repairing anything but are very adept at replacing components. Interesting comment that they broke the tranny housing
while they were attempting a ring job. I would have loved to seen that Exlax movement! (Yeah, another inch higher! oops !)

Well, take satisfaction that they didn't abuse your car trying to replicate the problem ( usually the green light for a tech to do as he will with your car) Did they grin when they said they couldn't replicate the problem? It's not bad enough to isolate? Good luck.

Personally, I wouldn't waste my time, even if the eventual repair work was covered.

 

I agree that this is typical dealer behavior. If I understand what you are saying, the folks at the dealer took your car for a test drive and heard a sound that they admitted was not normal. To my way of thinking, that is an admission that there is a problem. For them to say that the problem is not serious enough for them to look into it is totally unacceptable. I would write the dealer, confirm all of the facts, and demand that they service the car and find and fix the problem. If they refuse, I would take the car to a Corvette specialty shop and ask them to take a look at it. If they are able to identify the problem, I would again go back to the dealer and demand that the problem be fixed under the warranty. If they refuse, I would have the problem fixed by another reputable mechanic, get that work fully documented, and then file a small claims action against the dealer. I've said it before and will say it again, filing a small claims action is a very, very simple procedure.

 

They did admit there is a problem. I made sure that the service record from my visit to the dealer confirmed that they did hear the noise and that they advised me to wait on the repair.

Their problem, evidently, is that they are not able to diagnose the problem. I agree this is unacceptable.

At the same time, I don't really want to leave the car with them for a week while they, say for example, replace the layshaft main bearing, get the car back and then find out that the noise is still there. Schedule another appointment, leave the car again, wait for parts, etc. Repeat.

At some point, before the end of the warranty, I am going to have to bite the bullet and insist on the service. During the winter is a better time to be without the car.

If they won't do it then, will have to take some action, as you suggest.

If the dealer gets GM warranty approval for a particular line of repair, carry it out and then find that doesn't fix the problem, who pays for the mistake? It isn't the customer covered under GMPP... its the dealer or Chevy. I think that's their problem.

thanks,

-ag

 

Ok. One last try. Would still like to have a clue about what the problem is before taking the car back in for service.

Any ideas appreciated.

Here's a summary of the symptoms of this whirring noise which emanates from the gearbox:

o the noise only occurs when the car is in gear.

o the noise occurs regardless of whether the clutch is engaged or disengaged

o the noise is proportional to road speed, not engine speed


In addition, I've noticed recently that, when shifting the car into a gear, the noise starts as soon as the lever begins to move into gear, before moving fully through the synchros.

In other words, coasting along, with the car in neutral and the clutch depressed, the noise can be exhibited just by pushing the lever (from neutral) softly against the synchronizers in any of the gear positions. Doing so causes the whirring noise to 'spin up'. The frequency of the noise is highest in low gears and increases with road speed. It is very noticable (read annoying) in first through third, detectable in fourth and barely noticeable in fifth and sixth.

-ag

 

hmm sounds liek same problem i had, rear gears were going out and replace with new carrier and no noise

 

Antigrav,

Being an ex-gm employee, I know the system pretty well....Many dealers don't have the people to do this right. Many tech's are just remove and replace guys, they really don't know how to do anything more than that.

Since you are in a big city I would first get on the phone to several other Chey dealers. Talk to the service manager (not just the service writer) and find out if he has a really good manual tranny tech on his staff. Describe your problem and let him know that you want to get this fixed. Tell him you are pretty convinced that the car has a problem in the layshaft system (use the info below). It is pretty important that you sound knowledgeable. If he figures that you are a pretty savy owner, he isn't going to just blow you off. Explain that you had it to another dealer and that the really didn't appear to have the expertise to fix it. Most service managers don't want to get in over their heads, so if they don't have a good tech they will say, gee, you better take it to "so and so" because they have a guy there that can probably get it right. Also, ask your local Corvette club for a recommendation, as to a dealer, they know who has their act together. The NCCC likey has a listing on the web that can get you in touch, after a couple of calls you will be talking to someone who has built dozens of these things for racing and knows just what is wrong..

Once you find a dealer, take the tech for a ride and demonstrate for them what is happening. If the guy knows his stuff he is going to agree and at least take it apart to look at it. At that point bearings are cheap and if they replace the two bearings on the layshaft it will likely cure the probelm.

If you can't get anywhere with a simpathetic dealer, make an appointment with the zone service rep. You can show him the problem and get some action there. Remember that they want you to be happy, and this is not a cheap car.....

The additional info, that the noise accererates as you push the gear lever points directly to something in the layshaft. Since the noise is not pronounced at low engine speeds (with the engine idiling and the car in netrual and the clutch out) and it comes on as you push the lever (pushing the lever causes the synchro's to accelerate the layshaft so that the speeds can be matched and the gear engaged) all point to something in the layshaft, since that is the part that is changing speed as you push the lever.

You didn't mention if there was any gear in which the noise didn't occur. This would point directly to the bearing in that specific gear. Since it sounds like it happens in all gears (you even mentioned 5th and 6th), it is more likey a problem with one of the layshaft support bearings.

Good luck...

 

This is exactly the same issue that I have with my transmission. You've described it to a T. I also agree that it's something in the layshaft after doing the following test:
If driving at say, 50 kmph, and you take the car out of gear, and let the clutch out, the noise goes away. As soon as you pull the gear lever to put it back into gear, the noise comes back, regardless of what gear you choose. I just had my transmission rebuilt (syncros, forks, blockers...etc) and it did not solve the issue. Time to look at the bearings I guess.

 

You do realize this thread is 11 years old, right?

 

What relevance is that and what is the purpose of your comment? I never owned my car 11 years ago, and the issue only started happening in the past year. I'm sure I also won't be the last to have this issue either. Information from years' past does not "expire" and is still useful today.