Knock from clutch

[bigben5054]

Have a 79 K20 SM465.  New clutch, turned flywheel, new pilot bushing, new throwout bearing, new clutch fork.  Knocking sound coming from clutch area at idle.  Goes away when push clutch in.  Let clutch out and comes right back.  Started recently (not right after all new stuff was installed).  Thoughts?

[JohnnyPopper]

Sure it's not coming out of your transmission?

Do you hear it when you're driving?

[bigben5054]

I suppose it could be coming from the transmission.  I have not driven it to see whether it happens while driving.  I did some other searches and found some people talking about a knock being caused by improper clutch adjustment.  If memory serves, I think my problem started after I messed with trying to adjust the clutch.  When I get some time, I was going to fiddle with that a bit more and see if it helps. 

[Customdeluxe81]

Does it make the noise with the clutch out in neutral?? Mechanical clutch or hydraulic? Does your clutch “grab” at the floor or more at the end of the clutch pedal travel??

[JohnnyPopper]

I suppose it could be coming from the transmission.  I have not driven it to see whether it happens while driving.  I did some other searches and found some people talking about a knock being caused by improper clutch adjustment.  If memory serves, I think my problem started after I messed with trying to adjust the clutch.  When I get some time, I was going to fiddle with that a bit more and see if it helps.

Clutch alignment is not a variable, it only goes in one way-the correct way...
I have seen where a shop put the friction disc in backward, only to find the gearing shear under heavy load.
The q from CD81 is interesting-Neutral?

Look forward to your continued investigation............

[bigben5054]

Thanks.  I still haven't had time to mess with it.  To respond to other inquiries... Yes, it makes the noise in neutral and no foot on clutch pedal.  When I push in the clutch pedal, it goes away.  I didn't mean clutch alignment, I meant adjustment.  Meaning that threaded rod attached to the z-bar underneath the truck.  I think I need to read up on how to adjust that rod properly.  I am thinking it is probably too far in right now.  It's a regular clutch - not hydraulic. 

[Customdeluxe81]

Big Ben, to adjust a manual clutch you first remove the return spring, then check pedal “free play” meaning the distance the clutch pedal moves before you feel tension starting on the clutch pedal. Adjust the threaded rod clutch adjustment until you feel about an inch of free play at the clutch pedal then tighten the nut on the clutch adjuster and put the return spring back on and give it a go!
Hope this helps.

[JohnnyPopper]

Thanks for the added info. So look, in a correctly adjusted clutch:

Trans in Neutral with the clutch out transfers motion to a small part of the transmission.

Pushing clutch in disengages those parts from spinning.

Clutch pushed in-no noise because nothing in the trans is moving.

Clutch out in Neutral noise-noise is coming from the transmisson.

[bigben5054]

thanks custom.  By "return spring" do you mean the one inside the cab under the dash attached to the pedal?  That's the only one I have at the moment, but I know there is at least one more spring (perhaps 2 more) that go underneath to attach the Z-bar to the clutch fork and the clutch fork the the frame.  I don't have those and am getting mixed info as to whether either of those springs are actually necessary.

Thanks Johnny.  You logic makes sense.  I'll get the clutch pedal adjusted and drive it around some to see if anything changes.

[Customdeluxe81]

Big Ben, the spring near the adjustment. If I get a chance I’ll look in the manual for my 1981 and see if there is a pic and post it. You need sufficient spring pressure to keep the throw out bearing off the pressure plate. I just recently bought a clutch kit for my 81 and it came with a very cheap throw out bearing that had a bearing pressed onto a PLASTIC housing, I went to Napa and got the bearing that had the metal housing. Did your kit come with a similar bearing?

[bigben5054]

Mine came with a pretty heavy metal bearing.  I don't recall getting the feeling that it was cheap at all.  So if I'm not using the spring that keeps the throw out bearing off the pressure plate, perhaps that is what I am hearing.  Maybe the throw out bearing is riding on the pressure plate making a racket.

[Customdeluxe81]

Should have two springs at the clutch adjustment one small one between the clutch fork and the Z bar to keep tension on the adjustment rod another between the clutch fork and the frame to keep tension off the throw out bearing. Give it a try