Muncie Trannie noise?

[74 454]

Have original 74 454 with close ratio muncie, all never been rebuilt. 82,000 miles. Trannie has a growling noise coming from it when engine is at idle and clutch is out. Goes completely away with clutch down. It seems to get twice as loud after an hour or so of driving. I replaced the gear oil last year. Old oil looked fine and at full level. Previous owner said he has replaced the clutch twice. Is it possibly throw out bearing noise? Is clutch assembly getting ready for replacement?

 

[wishuwerehere82]

Sounds like a throwout bearing to me.
A good test is to listen for the noise at idle, then depress the clutch slightly so that there is pressure on the bearing but not enough to disengage the clutch. If the noise stops, you have found the problem.

 

[Hib Halverson]

If the owner has replaced the clutch twice, it's unlikely to be the TO bearing unless the clutch was replaced twice but the old bearing was retained. In that case, I'd replace the TO bearing.

But....the noise is more likely coming from the trans which probably has a bearing or bearings that are failed or failing. My guess is that a transmission overhaul is required. Do it sooner than later because the longer the trans is run in that condition the greater the damage is going to be.

 

[magoo]

Hib is giving you good advice on the sooner than later. Could be the roller bearing on the input shaft, or the needle bearings between the input shaft and main shaft. If properly adjusted, the TO bearing should not be turning with the clutch out.

Mike

 

[Crimson Thunder]

Something simple to check first.Make sure your clutch return spring is hooked up.Mine broke once and it made the TO bearing make the growling noise you describe.

 

[74 454]

Sharkcar71,

If the clutch return spring was not hooked up, wouldn't the clutch pedal stay down at the floor? Or is this a different spring all together down by the clutch and trans? Sorry, first time owning and working on a manual trans. I'd like to check for this.

Thanks to everyone else too for your advise! I'm going to try all your tests.

 

[Crimson Thunder]

The pedal will still come up but it will have no freeplay.The spring is located under the hood where the clutch adjustment is.

 

[74 454]

To all,

Checked the fluid this weekend and a good half of it was gone. Looks like the rear main seal, all wet. But don't know if front seal is leaking also. Didn't spend much time. Lower drain plug had metal shavings on the magnic, completely coated about 1/8" thick. Drained fluid and replaced with 85w140, instead of 80w90. Thought that would help with the high heat it runs in with the big block. Growling noise decreased alot. Probably back to where it was early last year when I first got it.

Tried the test of just pushing down the clutch a couple inches and growling continues. Only until the clutch is all the way down, and the trans stops spinning, does it go away completely. I'm sure a complete overhaul would do it, but for now I'll monitor the fluid and noise level. I may try replacing the rear main seal over the winter if it looks like this is only where it's leaking. My brother said I should replace the yoke too because it will most likely have a grove in it. The seal will not be large enough to properly fill the gap. Sound like a common problem?

I will eventually pull the trans for a complete overhaul, just don't have unlimited funds. My plans for the winter was to replace the leaky radiator, broken fan shroud, water pump, fuel pump and leaky heater core. All are original 1974. But if it gets worst, I may not have a choice.

I know, welcome to owning a old corvette! Wa Wa!

Thanks again everyone.