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What's this noise?

iamdave0887

iamdave0887

Here Comes Chaos.....
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http://www.youtube.com/watch?v=i0BuqnkwAxM

You can hear it right around 1:33 or so. It's a groaning/moaning sound.

I can't figure it out. It started doing it about a week ago after a week of heavy rain/high humidity. It doesn't occur every time. Maybe 50% of the time, and the rest of the time it's silent.

The pedal feels perfectly fine. No air, no binding.

When the noise occurs i can feel it in both the pedal and the shifter and it's there and gone in under a second. The only time the noise will "stay" longer is if i feather the clutch pedal(basically beginning to stall it in gear but then letting up before the engine stalls out).

It's only when bringing the clutch pedal back up and in gear. No load on the clutch and the noise doesn't show it's face.

I can stall the truck in gear so i know the clutch has a good bite.

I've heard everything from "run it" to a contaminated clutch disc.

How can the disc get contaminated after it's been installed though?

There's not 3,000 miles/3 months on this clutch/pressure plate/TO bearing, and the flywheel was cleaned up at a machine shop before this new clutch went in. The flywheel was brand new out of the box when i did this conversion back in 2009, and has maybe 1K tops on it since then.

Since i don't have much of a choice i'll run it for now, but would like your opinions on what the hell that noise is.

Thanks,

- Dave
 
the only parts that are moving are the throwout bearing and the clutch. my 2 cent guess would be the bearing. as far as a contaminated disc could happen if the valley drain tube is damaged or missing
 
Clutch shudder?

Pilot bearing and throwout bearing are the only spinning bearings. Drag on the clutch would be the only other noise sources. My concern would be the pilot bearing causing damage to the input shaft. You may have a broken finger on the flex plate - new just means it has a warranty... The input shaft bearing being loose also comes to mind.

Very rare, but, I have heard of it: the thrust bearing in the engine shot allowing the crank pulley to travel too far forward hitting/rubbing on something.

The noise is getting worse and this is a GM trademark - plenty of noise and warning before you walk. I would tear it down and find out what it is because of GM's warning and not wanting to hurt other parts.
 
There's a pilot bushing so the bushing being of soft metal will crush to dust before the input shaft tip is damaged one would think.

Perhaps it's a hard spot in the friction material. There was never a "pop" or anything like that before this noise began. It just started out of no-where.

The kicker is it's only when the trans is in gear. In neutral i can sit there and push the clutch in, hold it for a second, then let it out and get nothing. even if i pump the clutch, no noises at all.

Engine off, pressing the clutch results in no strange noises that would otherwise be drowned out by the engine.

I"m going to keep driving it, then monday on my day off i'll be pulling the slave cylinder out and removing the rubber boot around the clutch fork and looking in with a flashlight to see if i spot anything that would throw a red flag.

It shifts perfect still, and doesn't slip at all. This morning i came up to a hill, where i normally keep in in 2nd, i dropped it to direct(3rd) and hit the gas. No slippage. Engine lugged right down and started blowing soot clouds from the tailpipe, so i know the clutch has a very good bite.
 
With the headphones on I hear the rotary vane fuel pump... Doesn't sound like it going out.
Does this engine have an EPR on it? I had the vac line burn off this on my 88. Maybe this is the 'hiss' by being partially closed?

The noise is at engine RPM. Sounds like a bearing or something in the clutch that is engine speed vs. a stopped part. I take back the clutch shudder...
 
i'm wondering if it's just a "hard" spot in the clutch material. Like brake pads sometimes you'll get a spot that'll squeal when the brakes are applied, which is the pads vibrating more or less. Make the friction material 12" in diameter and and something that size won't speak, it'll groan.

That's my theory anyways. Not sure if it makes sense, hell this noise doesn't make any sense.

Yes there is an EPR, but it's been disconnected forever, and it's wide open. That pump you hear is a Holley Blue. Noisy doesn't begin to describe it.
 
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