66 l36- m21 trans noise

[Greg W.]

I had the clutch fork replaced and now have a whining noise with the pedal out. No noise with it in. Do not recall it befor the work was done, but the car is new to me.

Any thoughts, Thanks

[Mike T.]

Re: 66 l36- m21 trans noise

Greg - I see it's your first post, welcome. I get the feeling you had the work done, did they put in a new throw out bearing? Not that a new bearing would automatically be the cause of the sound but just trying to narrow down the list of suspects. The other thing that comes to mind is did whoever did the work attach the TO bearing the correct way? If it was a shop that's done auto repairs, you'd expect they'd now the diff. If it was someone who's kinda new to it, they could have done it wrong.

[John H.]

Re: 66 l36- m21 trans noise

I had the clutch fork replaced and now have a whining noise with the pedal out. No noise with it in. Do not recall it befor the work was done, but the car is new to me.

Any thoughts, Thanks

Greg -

The clutch fork and throwout bearing were designed such that they can be assembled incorrectly; most shops that know Corvettes are aware of this, and shops that don't know Corvettes probably don't. Two other possibilities are that the fork retainer spring isn't fully seated on the pivot stud, and the linkage isn't properly adjusted with 1" of pedal free play at the top of travel.


TOBearingInstall2.jpg

[Greg W.]

Re: 66 l36- m21 trans noise

Thanks Mike, it cant be the to bearing, there is no noise when the pedal is in. A corvette shop did the work. Just think it sounds like its in the trans,but that was not gone into. Does that help any, thanks

[Greg W.]

Re: 66 l36- m21 trans noise

John, When I push the clutch in and the TO bearing is spinning there in no noise at all

[Steve G.]

Re: 66 l36- m21 trans noise

If there is no noise with the clutch pedal down (best checked with trans in gear so that disc is not spinning) but makes noise with clutch engaged (pedal up) it is not the release bearing or the pilot bearing. This is true provided you have ample free play in the pedal so that you are certain that the release bearing is clear of the clutch fingers.

If engaging the clutch with the trans in neutral brings the noise on the possibilities are the input shaft bearing, the bearing where the output shaft runs inside the end of the input shaft, the counter shaft (cluster gear), 1st, 2nd or 3rd gears on the main shaft or the reverse idler. All those are in motion with the car stationary, trans in neutral and clutch engaged. Of those the most probable is the input shaft brg or the counter shaft. It's also possible to have gear noise. These are constant mesh transmissions so everything is turning, just not locked to the output shaft.

Long and the short, whatever it is will be apparent to whoever does the overhaul.

Steve

[Greg W.]

Re: 66 l36- m21 trans noise

Steve, Thanks for the input. I am trying to figure out how this noise just started after the TO bearing,clutchfork was only replaced. There is not a lot of noise of noise when in neutral but I think to much .

[Steve G.]

Re: 66 l36- m21 trans noise

Steve, Thanks for the input. I am trying to figure out how this noise just started after the TO bearing,clutchfork was only replaced. There is not a lot of noise of noise when in neutral but I think to much .

I suspect it was always there. If the to brg was replaced because of noise it was probably masking the other noises. Additionally, whenever a repair has been done we tend to pay particular attention to the area of interest and start to hear things we didn't notice b4. The only other change I could think of would be the pilot brg, as in they forgot to put one in. Of course this alters the alignment of the input shaft with the weight of the disc pulling the input shaft down. It would have to be the brg missing tho, not a faulty or new one installed because we know the bearing itself (assuming it is there) is for certain not defective.
Steve

[Michael C.]

Re: 66 l36- m21 trans noise

My m-21 was making the same noise. Last season I replaced the pilot bearing, TO bearing and adjusted the free play. Noise was still there. This winter I pulled the teams in did a full rebuild. New bearings, new sliders,hubs, synros,replaced counter shaft and needle bearings. I haven't fired it up yet to see if the noise is gone yet. Rebuild was rather easy.

[Domenic T.]

Re: 66 l36- m21 trans noise

Greg,
There is a tang riveted to the fork. If the pedal adjustment is not correct the bearing will turn rubbing this tang and make noise. That bearing race where the fork is, is not supposed to turn against the fork but with thick grease that bearing race will try to turn if there is not enough free play. When the pedal is pushed down it would stop that rotation. That can be fixed with a simple adjustment.
If needed, you can peek in with the boot removed but that would only be necessary if you suspect the fork was not installed correctly.

DOM

[Greg W.]

Re: 66 l36- m21 trans noise

Dom, This could be the problem and would make sense because it only started after the fork was replaced.

Thanks Greg

[Steve G.]

Re: 66 l36- m21 trans noise

Dom, This could be the problem and would make sense because it only started after the fork was replaced.

Thanks Greg

I'd be skeptical of that because if the pedal is properly adjusted the release bearing is not in contact with the clutch release fingers and there is nothing to turn anything. So the release bearing will not turn at all, either turning as it's supposed to or the outer race turning in the fork.

To confirm thise simply further adjust your clutch so that you have an excessive amount of free play. You now have the release bearing well away from any spinning component.

These are not constant running release bearings as are found on some hydraulic self adjusting clutches. These bearings are not supposed to touch the fingers when not in use and if they do they will not last long. This is why we have the free play in the pedal and springs pulling the fork away from the rotating clutch.
Steve

[Domenic T.]

Re: 66 l36- m21 trans noise

Greg,
That was a shot in the dark but I think Steve agrees on part of my post about the proper adjustment. If the face of the bearing is touching slightly from a bad adjustment, or spinning, the new grease will turn the rear race such as a torque converter turn using oil.
I would agree that you adjust for free play and see what happens. As said nothing should turn at the fork. Also there are clutch rod return springs that would allow a properly adjusted fork return to the pressure plate. That is common when the springs are not attached to the fork or clutch rod. Those springs are there for that reason only and hold the pedal up. If you have to lift your pedal up to check the free play that would be your first clue. A visual will tell you if your spring or springs are missing.

Dom

[Steve G.]

Re: 66 l36- m21 trans noise

Greg,
That was a shot in the dark but I think Steve agrees on part of my post about the proper adjustment. If the face of the bearing is touching slightly from a bad adjustment, or spinning, the new grease will turn the rear race such as a torque converter turn using oil.
I would agree that you adjust for free play and see what happens. As said nothing should turn at the fork. Also there are clutch rod return springs that would allow a properly adjusted fork return to the pressure plate. That is common when the springs are not attached to the fork or clutch rod. Those springs are there for that reason only and hold the pedal up. If you have to lift your pedal up to check the free play that would be your first clue. A visual will tell you if your spring or springs are missing.

Dom

I agree fully Dom. In fact, sometimes when the adjustment is just a little too close the bearing will just skim the rotating fingers without even enough pressure to turn the bearing and what you hear is the finger slipping on the surface of the bearing. And when the adjustment is that close, you do feel free play at the top of the pedal.

Steve

[Greg W.]

Re: 66 l36- m21 trans noise

Dom & steve, This gives me something to start with. I checked the pedal , and clutch rod movement, backed off on the adj. nuts and there was no freeplay at all. Could not tell if the bearing was touching the fingers until I start it up. Need to let it stop snowing to pull it out. Will let you know.

Thanks for the help, Glad to see people still help
Greg