R66

Left home and all was fine. Drove about 30 miles and parked the car for 1/2 hour. Started it and when I let the clutch out in neutral, got a squeal like a fan belt on a locked up alternator. Squeal ceases when clutch pedal is depressed enough to make contact with the pressure plate. Also ceases when the clutch pedal is lifter with my toe to tighten it against the stop. Moved the car to the bay with the lift and no squeal with pedal in any position.
I have about 1/8" clearance between the release (throw out) bearing and the pressure plate diaphragm fingers, so how can I get a squeal with no contact? Also why is it intermittent?
Took a picture with a borescope, but cannot get it off the phone.
Any ideas before I rip the transmission out?
Ideas needed,
Thanks, Ron

66jack

Could be the input shaft...it spins continuasly..

Tom Austin

I had a similar situation with a transmission I just took out of my '66 . . . it turns out that the ball stud in the bellhousing was loose! Good luck!

Tom

R66

Never thought of that, I'll check it out. It could be moving around and changing the clearance on the release bearing. Thanks, Ron

66 Jack - Could be the input shaft...it spins continuasly..
Possible with wear in the pilot bushing allowing the input shaft to spin off center, but the sound is more like sever belt slippage squeal and goes away with light pressure on the pedal. If I have to pull the Muncie, it will be on the inspection list. Thanks, Ron

Linkage at rest. 1/8" clearance. Haven't tried to run engine while on my old lift.

DansYellow66

It didn’t squeal with the clutch engaged and the transmission in a gear (moving)?

R66

No, just in neutral with the engine idling. I swore it was the alternator belt and a bad bearing in either the alternator or water pump, but removed the belt and still had the squeal.
Going back into the garage to work on it now and check the linkage joint by joint before I start tranny removal.

Westlotorn

The picture does not seem to show any grease being lost from the throw out bearing? I would think if it was failing we would see signs of the grease getting out.

tuxnharley

Sounds like it might be a bad pilot bearing? What kind is in there? How old?

jforb

Bad pilot will only make noise when the clutch is released (pedal pushed down all the way).

Is there any play on the fork? if the pivot ball is loose or the clip is gone, it will move around and let the bearing contact the pp when the pedal is up.

R66

More confusion!!
I checked the linkage from the pedal to the fork - all tight and good.
I taped the borescope to a magnet and mounted it on the clutch fork to see what the throw out bearing was doing. I started it and ran it in neutral on my lift, no noise.
Then exercised the clutch pedal with the engine running to try to duplicate the noise - no noise in any position.
I checked the lubricant in the Muncie - up to correct level. No leakage at the rear seal.
Odd video with engine running - appears input shaft is not turning when clutch engaged and in neutral ??? Has to be an optical Illusion as car drives normally??? I can't upload the videos as they are the wrong file type and I am not AI knowledgeable.
The noise only occurs with the clutch engaged and the transmission in neutral. No noise with the pedal depressed to release the clutch in any position. There is play in the fork if I twist it, but it seems normal as the spring clips return it to position. During the run video, the throw out bearing is not touching the pressure plate and remains about 1/8"+ clearance.
Looks like I may be pulling the Muncie just to continue the troubleshooting.

jforb

In neutral, clutch released, almost all the bearings and bushings and gears in the transmission are turning...could be in there.

You can't really see the input shaft when it's all assembled, it's hiding inside the front bearing retainer, which is the tube that the release bearing slides forward on.

Mark in MN

Our 66 was doing the same thing a couple weeks ago. 6500 Miles since installing a new clutch, throughout bearing and pilot bearing. Pilot bearing had failed, stuck to the transmission shaft, and started to spin in the crankshaft. Turns out the "HD" National bearing was just a chunk of solid metal.
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R66

The input shaft and counter shaft are indeed spinning with the Muncie in neutral and clutch engaged. I am starting to agree with the problem being in the pilot bushing or the input shaft bearing of the Muncie as the sound is intermittent, varying in intensity when it occurs. Maybe the pilot bushing is worn and allowing the input shaft to ride on the inside of the input housing / nose. If it is the release throw out bearing, it would be consistent rather than intermittent and would make noise when in contact with the pressure plate, not when at rest.
I can see the input shaft spline with the clutch engaged and pressure plate spinning, and it appears to be not turning, yet I know it has to be as the car drives well in all four gears and the input drives the countershaft. It is an optical illusion seen from old eyes.

R66

I hate to think it, but I replaced the clutch with pilot bushing and throw out bearing about 4,000 miles ago, so it could be the assembly. I used the brass pilot - nonmagnetic as I have had the pilot eat a input shaft in the past.
I keep getting closer to a teardown to find the problem. I have enough spare parts to replace everything, but no longer have the enthusiasm I had 40 or 50 years ago.

Dan Hampton

I don't think it is transmission-related. You would hear a "growl" with a bad input bearing. My bet is the pilot bearing. One question, however. Is this an OEM bellhousing? The fact that you tore up one pilot and, now, it might be a repeat, would tell me there is an alignment issue with your input. How does it shift going into 4th?

R66

I think you may be right Dan. It was a different vehicle and transmission which I lost the pilot 'bearing' in. It ate up the input shaft on a DNE 5 spd many years ago.
The bellhousing is indeed OEM and the drivetrain has over 130,000 miles on it. It is our 68RS Camaro, not R66 Corvette. It is much easier to pull the tranny on the 68RS than R66, the only good thing at this point.
The Muncie shifts fine and no problem jumping out of 4th which I might expect with the input shaft bearing moving around.
Thanks,
Ron

jforb

I recently had to replace the pilot bushing in my 62, which has an early M20 in it. It made noise only when the clutch was pressed, car not moving, transmission in gear. In other words, when the pilot bushing is actually doing something.

I replaced it with a bronze (non magnetic) bushing. The one that went bad in less than 10k miles contained iron.

One thing about Muncie transmissions, you'll find a new problem with one every time you take one apart

R66

Yea, back to the beginning again: In neutral with the engine running, clutch engaged (pedal up), squealing noise until I push the pedal in to barely touch the pressure plate would not release the clutch to allow the pilot shaft to recenter. Also lifting up on the pedal would not stop the squeal. I have more than 1/8" clearance (1" free play on the pedal). It is an intermittent problem. Linkage is tight. Clutch fork aligns well on the pivot ball and the throw out bearing is properly held by the fork.
I am back to thinking the throw out bearing is the problem, but if it is dry of grease it would squeal all of the time and only when in contact with the pressure plate. Also, it doesn't spin when not in contact with the pressure plate.
Won't work on it tomorrow, I have a couple of VA appointments tomorrow, will give me time to think some more.
Thanks to all for the ideas.
Ron

DansYellow66

I don’t see how it could be the pilot bushing when idling in neutral with the clutch released (pedal up). The input is locked in to the engine and with the free play the TOB would not appear to be spinning. That pretty much leaves the front bearing or needle bearing inside the input or some unusual metal to metal scraping inside.