I'm getting some gear whine when I deep into the power in first and second. Not much, and if the radio is on you can't really hear it, but it sounds more like a racing crash box at high rpm and high power?

Car is a C5Z, has 22,000 miles on it, a couple of seasons of autocrossing, but nothing in the last year or so. No signs of fluid leaks or any loss of fuid, and not sure if it's the diff or the gearbox, but it seems more like the gearbox based on the frequency of the tone in each gear (not the same tone after I shift, where it would be the same tone if it was the diff)

Thoughts?

 

Other than disassembly and inspect OR electronic monitoring each gear case for noise with a transducer to see which one it is, theres not much you can do. I would drain and fill each gear case and inspect the old oil for any signs of worn parts.

 

Bill,

Thanks, sounds like a plan...

 

I was getting some gear whine a while back and it Only got worse. I went to RPM to have it rebuilt before it ate itself. Turns out I had broken clutch packs, a worn gear, and my hardened shaft was bent. Gear whine means something is wrong.

 

If it is the axle you will hear it in 4th gear also, if not it's the transmission.
With a few seasons of auto X on it I'd bet your looking at replacing 1st and 2nd speed gears along with the countershaft at a mininum.
Changing the oil may help it live a little longer but once you start to break through the case depth (hardness) of the gears the profile goes away quickly.

 

I have seen road race/auto cross trans having issues with noise especially when using slicks. The fluid moves around so much so that it doesn't have a chance to lubricate the gears during high sustained G's. This condition causes the gears to overheat and in turn changes the clearance between the mainshaft gears and the cluster shaft. The C6's and C6 Z06's have fluid pumps on the midplate to shoot fluid to the gears. Up to 08, the port was near the 2-3 gears but starting 09, the port was moved toward the 4th gear. Unfortunately you have to replace the gears/clustershaft to repair the noise. IMO, it's better to just replace the unit since it would be cheaper. The clustershaft alone is over $1,200 new.

 

Car hasn't been driven in anger in two years, and the noise is recent. More noise in first than second, so I'm of the opinion that it's the gearbox for sure.

I talked to a good friend who is an engineer at Tremec and he is going to talk to the engineers who work the six speed and he is going to suggest a plan. Not sure if it's a bearing or gear wear, if it's a bearing then need to fix it before it does any more damage.

Will change the lube tomorrow and see what happens.

 

Solofast,
Pls post your progress on this. I may be having the same problem slowly developing.
Thanks,
Will

 

Changed the fluid to Mobil 1 ATF. The only stuff that Autozone had was the Dextron replacement for 2005 and older cars. They didn't have the new Mobil 1 for later than 2005. If they had had that I'd have used it, not sure what the difference is, but it's supposed to be "better" even in the older cars, or so that's what Mobil says.

Anyway, the whine is gone in first and second, so the fluid change most definately helped. I tried it out and made sure that the box was well warmed up and there isn't any noise. Fluid was pretty dark. I would have thought that it wouldn't have gotten that black since there isn't any combustion crap in the gearbox. One thing that blackens oil is oxidation. With the exhaust pipes that close to the gearbox it is going to get pretty warm and over time it ruins the fluid. Automatics all use oil coolers in the radiator and that tends to limit the fluid temp unless you are abusing it. Six speeds don't have that cooling so things can get awfully warm.

While GM doesn't recommend a fluid change interval for the gearbox, it probalby isn't a bad idea to change it more than occasionally. From now on I'll change it every other year or at about 10k miles.

Can't hurt.

I'll post anything I learn from the Tremec guys.

 

The black stuff is the compressed carbon blocking ring friction material. They do wear over time. Let us know if the noise returns.

 

Got some feedback from Tremec...

The Tremec guys say that this box is very robust and almost never breaks, unless it is seriously abused, run without oil or hammered on, it doesn't break.

The first question that they asked was the box fully warmed when it when it was noisy (the answer is no it probably wasn't all that well warmed, it had only been run about 8 miles or so)? They said that the clearances open up some because the aluminum expands more than the steel in the shafts, so it's important to warm it thoroughly before you stand on it. Since the noise was gone when I made sure it was well warmed, I'm thinking that was most of the issue.

One other thing they mentioned was that the rubber isolators in the linkage sometimes wear out and when they do, there is a lot more gear noise transmitted into the cockpit. That isn't the case here, but if you hear some gear whine don't go digging into the tranny unless you are sure the linkage isn't worn.

They did say that fluid makes a difference in these boxes. The factory fill is optimized to reduce drag and give adequate life, but there are better fluids out there. Their recommendation was to use Pennzoil "Synchromesh" in applications like racing where stress is higher and added lube properties are needed. Don't want to get into peeing contest as to who uses what lube and which is best (ie, Deadline, Mobil 1, Poyal Ruple ect...) Just passing on their recommendation.

Hope that helps anybody else who is having the issue, make sure it's really warm first and then see if the noise goes away before you start worrying about it.