# After Clutch Replacement: Loud Whirring/Rubbing Sound When Letting Out the Clutch to Take Off



## Spalding (4 mo ago)

I’ve just replaced the clutch in my 1966 GTO, 4 speed Muncie, 389. There has been some shimmering on take off. The clutch was worn down, there were burn marks on the pressure plate and flywheel . I had the steel flywheel resurfaced. I got a new Duralast 11” clutch and pressure plate at AutoZone. The pressure plate I took out was a street McCleod. The pressure plate I put in, had fingers ~1.5” taller than the McCloud, when both uncompressed. The kit came with a new throwout bearing. I’m told it was a Chevrolet throwout bearing, but was the same size as the one I took out.
Now when I take off in first or reverse, there is a loud whirring/rubbing sound until the clutch is fully engaged (clutch pedal fully released). No sound with clutch pedal fully engaged. Sound starts when letting out clutch pedal until fully out. No sound if I push clutch in and out in neutral.

Does anyone out there have an idea of what could be the cause?


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## PontiacJim (Dec 29, 2012)

Spalding said:


> I’ve just replaced the clutch in my 1966 GTO, 4 speed Muncie, 389. There has been some shimmering on take off. The clutch was worn down, there were burn marks on the pressure plate and flywheel . I had the steel flywheel resurfaced. I got a new Duralast 11” clutch and pressure plate at AutoZone. The pressure plate I took out was a street McCleod. The pressure plate I put in, had fingers ~1.5” taller than the McCloud, when both uncompressed. The kit came with a new throwout bearing. I’m told it was a Chevrolet throwout bearing, but was the same size as the one I took out.
> Now when I take off in first or reverse, there is a loud whirring/rubbing sound until the clutch is fully engaged (clutch pedal fully released). No sound with clutch pedal fully engaged. Sound starts when letting out clutch pedal until fully out. No sound if I push clutch in and out in neutral.
> 
> Does anyone out there have an idea of what could be the cause?


Could be several things without seeing your set-up. Pilot Bearing or bushing? Was it replaced? Clutch friction material - may need to get worn in. Improper flywheel resurfacing - not level evenly re-surfaced. Clutch disc springs hitting the flywheel bolt heads if the wrong/high head bolts were used. With the higher pressure plate fingers on the new one is higher, sounds like you would need the short throw out bearing, but the position of your clutch fork angle should be the indicator. Pontiac factory style clutch fork and not an aftermarket generic "said to fit Pontiac and other GM brands"?

#1 Flywheel/crank bolts hit the disc spring and did some grinding - Made a strange whine sound when pushing in or letting out the clutch.
#2 Different throw out bearings, long & short. There is also one in between. The face that rides on the fingers should be correct for the diaphragm as there are different types.
#3 Correct and Incorrect angle/position of the clutch fork. If the angle is wrong, it could be the throw-out bearing is incorrect or the wrong clutch fork is being used.


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## Spalding (4 mo ago)

The pilot bushing was replaced. I took the flywheel to a reputable machine shop, as well as watched it being done. I believe it was correctly and evenly surfaced. The throw out bearing is the short one and the face very like the one I took out. It came as a kit, so I would think it should be the right face. I did nothing to the fork, but can take a look at the angle to try to validate it is ok. Three of the flywheel crank bolts were replaced. I don’t believe the heads were any thicker. The noise does not sound like metal on metal. Being springs, might it make a loud whirring rubbing sound? The rubbing sound is almost like rubber dragging sound against something. 

One thing, the crank bolts had been put in with some kind of lock tight and were not easy to get out. That’s why 3 had to be replaced. They did not have washers to lock the bolts. Should they have had washers to lock the bolts?

Thanks very much for your comments!


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## PontiacJim (Dec 29, 2012)

Spalding said:


> The pilot bushing was replaced. I took the flywheel to a reputable machine shop, as well as watched it being done. I believe it was correctly and evenly surfaced. The throw out bearing is the short one and the face very like the one I took out. It came as a kit, so I would think it should be the right face. I did nothing to the fork, but can take a look at the angle to try to validate it is ok. Three of the flywheel crank bolts were replaced. I don’t believe the heads were any thicker. The noise does not sound like metal on metal. Being springs, might it make a loud whirring rubbing sound? The rubbing sound is almost like rubber dragging sound against something.
> 
> One thing, the crank bolts had been put in with some kind of lock tight and were not easy to get out. That’s why 3 had to be replaced. They did not have washers to lock the bolts. Should they have had washers to lock the bolts?
> 
> Thanks very much for your comments!


Ok, sounds like everything is in order and you replaced what needed replacing and have the correct parts.

No, no lock washers on the crankshaft bolts, just torque them.

Here are pics of examples I found showing what I mean in the differences in the thickness of the crank bolt heads. I believe it is the ARP bolts that are too thick and the Mr. Gasket are the thinner heads you want. The Hays aftermarket steel flywheel is not as deep in the center as a stock flywheel because I assume the material is thicker in that area. The low profile heads have to be used or they can hit the clutch disc springs as I found out when I pulled my engine/trans out to do my ground up resto-mod. I went with a kevlar or carbon fiber (can't recall) disc material which I have never used. When letting out the clutch/slipping it, it has a strange sound which I can only describe as a medium pitched whine. I just figured it was the clutch material making that sound as I never used a kevlar disc - always the old style asbestos type discs. It wasn't until I pull the trans off the engine and the clutch set-up that I realized that the noise was not the disc, but the clutch disc springs hitting the crank bolts. The springs are a little worn down and shiny and the tops of the crank bolts were shinny.

Make sure the spring fingers of the clutch fork are located correctly under the collar of the throw-out bearing and not over/on top of it. Just another thing to check if not sure.

Not saying you have the same issue, just saying it could be a possibility.


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## armyadarkness (Dec 7, 2020)

I had the wrong flywheel bolts that Jim mentioned... if that's the case, man, it would be a noisy mess.


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## armyadarkness (Dec 7, 2020)

Also, if you turned down the original flywheel, then bolt thickness really comes into play!


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## Spalding (4 mo ago)

Thanks PontiacJim for the tips. I am going to tear it down tomorrow and see if I can tell anything. The bolt clearance, the fork arm angle. I’ll post with what I find.

If it’s not rubbing on the flywheel bolts, I’m wondering if the diaphragm fingers on the pressure plate being 1.5 inches higher uncompressed than the one I took out is affecting that angle of the fork angle you mention. Should that pressure plate still work?

Thanks armyadarkness. I need all the input I can get. Crazy!


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## armyadarkness (Dec 7, 2020)

You may take something away from this. It's very descriptive








FAQ - Powetrain: TREMEC TKX - Automatic to Manual Conversion


This is my final write up for the swap. It is NOT ANY CHEAPER to do a Muncie than a Tremec.. in fact, it's more expensive. A quality Muncie rebuild is going to cost over $2500 and you wont have overdrive. So, yes, you can buy a used cheap Muncie, but that's on you if you choose to forgo the...




www.gtoforum.com


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## PontiacJim (Dec 29, 2012)

Spalding said:


> Thanks PontiacJim for the tips. I am going to tear it down tomorrow and see if I can tell anything. The bolt clearance, the fork arm angle. I’ll post with what I find.
> 
> If it’s not rubbing on the flywheel bolts, I’m wondering if the diaphragm fingers on the pressure plate being 1.5 inches higher uncompressed than the one I took out is affecting that angle of the fork angle you mention. Should that pressure plate still work?
> 
> Thanks armyadarkness. I need all the input I can get. Crazy!


The taller diaphragm fingers should not be an issue. Some diaphrams have flat fingers and some raised - as you have. The length of the throw-out bearing is what compensates for this. So the flat fingers would have the longer bearing, raised fingers the shorter bearing. Your pedal throw is the same with either style as that does not change.

If you had a short bearing on a flat finger, you would be pushing in the pedal much farther before the bearing actually begins to push on the fingers. By the time you got the pedal to the floor, you would not be compressing the fingers enough to lift it off the clutch disc - so it would not engage, or would drag. The first thing most do, including myself when I did not know this in my youth, is to adjust/lengthen the pushrod that goes to the fork. That might get the disc to release, but the pedal will be almost at the floor to do so.

If you had the long bearing on the raised diaphragm, the clutch fork would most likely be up against the opening in the bell housing. If you could make it work, when you pushed the fingers in, you would most likely over extend the fingers and bend/break them. You might be able to adjust some of that out, but you would still be over extending the fingers and causing them to fatigue and your pedal would be way up top when you released or engaged the clutch pedal. 

If you read the instructions that come with most kits, there is a "air gap" number. This means that there should be an air gap between the clutch disc and flywheel and/or pressure plate. Someone has to push in on the clutch pedal and with the bell housing inspection cover removed, you insert a feeler gauge of the correct thickness between the disc and flywheel and adjust the clutch fork pushrod accordingly to get that air gap. I have honestly never done this. I simply adjust the fork pushrod to where I like the pedal height as it releases the clutch. Some like a low pedal and some like a higher pedal. I don't want it releasing off the floor nor at the top, so probably about 3-4" if I had to guess. But you can do the air gap measure to confirm that the clutch disc is separating from the flywheel/diaphragm and not binding or sticking and not sliding on the trans input shaft.


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## Spalding (4 mo ago)

PontiacJim said:


> Ok, sounds like everything is in order and you replaced what needed replacing and have the correct parts.
> 
> No, no lock washers on the crankshaft bolts, just torque them.
> 
> ...


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## Spalding (4 mo ago)

PontiacJim 

My car guy and I tore it down Tuesday. After getting the transmission out, we put a spline in and checked the fork/throwout bearing. The fork was at an acceptable angle with the throwout bearing straight. When pressing in the clutch pedal, the throwout bearing also went in straight and returned straight. 

We then took it down to the flywheel based upon the 2nd of your potential causes and found two things:


The springs were rubbing on the bolts as you mentioned as a possibility.
The inside metal frame of the clutch plate was flush with the clutch material and the rivets were rubbing on the flywheel. (see attached picture)
That particular plate was not for my application. Possibly the clutch plate is for a Chevrolet, but in many cases will work for Pontiac, so it is sold for that application? I will know to check this in the future.

I obtained a new LUK clutch with the center plate recessed, considerably below the clutch material and the rivets much flatter.

We took the bolts in the flywheel out, removed the washers and torqued them back in. We put layers of tape on the top of the bolts and put the clutch on the flywheel, rotated it and shifted it up and down to ensure there was no rubbing.

We put it back together and it works great.

Thanks for taking the time to review my post and provide your expert diagnosis. I learned a lot, as we really had no idea what could have been causing the noise, especially since it really didn’t sound like metal on metal. I’ll know to check these things next time. Hopefully this will help others not make the same mistakes.


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