Help! Cluch / Muncie whirring noise!!!

[Bolisk]

First of all, it's good to be back! After two years of no Corvette in my life, I'm finally working on the car again. Moving the family and having two small kids doesn't help with time in the garage.

Ok, so here is the problem. . .and this happens when the car is stationary with the shifter in neutral:

There is a whirring noise coming from the transmission / clutch area. At first I thought it might be the throw out bearing. . .but the behavior is not making sense. When the cluch is engaged (peddle released and fully up) it makes that whirring noise. However when I push the clutch in (clutch disengaged pedal fully down), the whirring noise winds down and stops. HOWEVER, the whirring noise does not stop until the clutch is fully disengaged. . .in other words, if you slowly push the clutch peddle down the whirring noise persists all they way down until the cluch please actually releases from the fly wheel. I would think that if it was the throw out bearing. . .then the noise probably would have stopped when the bearing started to get loaded on the flex plate fingers. But no, the noise persists at the same volume and speed righ up until the clutch releases from the flywheel.

I have a bad feeling it's the input shaft/counter shaft, or other constant mesh gears in the trans while in neutral. That seems to make the most sense to me as all those parts are spinning when the clutch is engaged. . .then they stop when you disengage the clutch.

The pervious owner swore up and down that the car had a M22 in it. But when I inspected the car, I showed him that the trans stamping codes showed that it was the numbers matching correct M20 transmission. So unless he had it rebuilt with M22 gears. . .it's an M20. He stopped being so sure after that lesson. Now I'm not so sure.

Is this whirring noise normal for an M22? I know my pervious car with an M20 didn't make this noise. . .

 

[dougelam]

What's in it for oil?
80-140 gear lube or something thinner


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[Bolisk]

Good question. I wanna say 75w 90. But I'm not sure that is correct.

 

[dougelam]

Muncie transmissions are known for noisy counter shafts, heavy oil insulates that

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[Bolisk]

I confirmed that it's Valvoline 75w90 GL5/4 high performance gear oil. This is exactly what I used in my other muncies with now issues, and no noise. I may try the heavier oil.

I sent an e-mail to Paul Cangialosi with the same question. . .and he indicated that it could just be noisy old gears, but that I should inspect the input bearing. I guess the trans is coming out.

-J

 

[Hib Halverson]

Reality is that Muncies, in good condition, are not "known for noisy countershafts". It is true that a heavier oil can sometimes "mask" trans noise, it's not a good idea to put 140 gear lube in a trans which requires a 90.

Any transmission makes noise, even when new. I say that because old cars sometimes have poorly-sealed shifter holes and rotted acoustic insulation under the console trim. If that's the case with this car, even a trans in good condition might be audible, but not because it's worn. It's because there are easy paths for normal noise to get into the interior.

That said, if the console still has some acoustic insulation and the shifter hole is sealed with the proper upper and lower boots, and you hear a constant whirring noise, then I'd say that either bearing or bushing wear has occured or the case has deformed allowing the counter shaft and the mainshaft to move slightly more farther apart. In some cases, that can increase noise, too.

As I said above, it is true that in some cases, you can go to a heavier gear lube, and make the noise less, but that does not repair the problem, it fools you.

On the lube...you say you're using a GL4/GL5 "multi-purpose" lubricant. Reality is that just means the lube is a GL5 which has an EP additive package intended for lubricating hypoid gear sets in drive axles. EP additives in GL5s interfere with proper synchronizer operation. Always use a GL4 lubricant in helical gear transmissions because it provides better shift quality.

Lastly, if you're in touch with Cangialosi, good move. He's "the guy" when it comes to Muncies.

 

[Bolisk]

Hey Hib, good to hear from you again.

For the most part I agree, generally I don't like to mask a problem with thicker oils. But to be honest, I wasn't 100% sure I had the right weight oil in there. I thought it was supposed to be straight 90, 75w90 or 80w90. . .but the seed of doubt was thrown, and I figured I would try that if I was wrong. Seems like I had the right weight after all.

Now, with respect to Valvoline GL5/4. . .I tried to do my homework there. I am aware you are supposed to use a GL4 in Muncies, but those are getting harder and harder to find at the local auto parts store. You can find them on line. . .but some of them are not very common brands. In my research into this I found a write up from Valvoline on their "High Performance Gear Oil". . .which I will try to dig up and re-post if I can find it. . .where they went into deep detail (I'm recalling this from memory) about how early GL5 oils added sulfates for the hypoid (something or rather) and these sulfates were known to eat up yellow metals (like the synchro's in our old Muncies). They went on to say that "their" high performance gear oil, while it meets the GL5 rating. . .it also meets / exceeds the GL-4 rating and will not harm yellow metals because they do not have the sulfate additives in their "high performance gear oil". So, if memory serves, their claim wasn't that they had an additive that protected yellow metals. . .rather they didn't put the additive in (that harmed yellow metals) in the first place. They went on to indicate that it was safe for use in Muncies, Richmond, and top loaders. I also noticed that the local corvette restoration shop ONLY used that gear oil. . .and it was the only gear oil that they would warranty in their work. So I figured that it was safe to use. So I feel fairly confident that this oil is a-ok. But again, I'm pulling this from memory. If I can find that write up. . .I will re-post so that others can see for themselves. Until that time. . .use with caution.

So, back to the problem at hand. . .this sounds more like it's coming from under the car. . .than through the center console. You also mentioned the possibility of warn bearings or bushings. What bushings?

The reason I was contacting Paul, was to talk about the other problem I was having. . .which I didn't mention in this thread. That being that my trans kinda leaks like crazy. Appears to be mostly coming from the shifter fork seals. So I was ordering his redline seal set. . .and getting recommendations for other things to do while I'm at it. I mentioned the noise and the conditions it occurs under. Those were his two thoughts.

Thanks again,
J

 

[Bolisk]

Damn it. . .looks like I was kinda wrong. According to these new sheets. . .it's this oil we should be using.

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[Bolisk]

Man, now I'm confused. The spec sheet for the high perfomace gear oil shows no (ZERO) sulfer. . .like I originoally remember seeing. And the vlavoline GL4 MTF or Syncrhomesh oil DOES have sulfur in it!!! I'd post their links. . .but I'm not sure how to do that in the forum.

-J

 

[Antz81]

Damn it. . .looks like I was kinda wrong. According to these new sheets. . .it's this oil we should be using.

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Working link:
http://content.valvoline.com/pdf/vps_manual_transmission_fluid.pdf

 

[Antz81]

Man, now I'm confused. The spec sheet for the high perfomace gear oil shows no (ZERO) sulfer. . .like I originoally remember seeing. And the vlavoline GL4 MTF or Syncrhomesh oil DOES have sulfur in it!!! I'd post their links. . .but I'm not sure how to do that in the forum.

-J

I just copy and paste from the address bar. Never had any issues doing that.

 

[2VettesMike]

I've got a 58K miles 72 with M20. Same gentle whirring sounds when the clutch pedal is out.
BTW, NAPA sells GL4 by the gallon jug.

Mike

 

[Crimson Thunder]

Don't forget to check the easy things first. If the spring under the clutch linkage is missing or broken the throwout bearing will make noise. Once I replaced mine the bearing noise went away.