# Knocking noise



## papereater (Sep 16, 2016)

People,

1987 Sunbird GT, 226,000 miles. Just replaced clutch a few months ago, first time. Car ran fine for a few months. Now I am getting a knocking sound at a frequency of about 8-10 per second when driving at about 50 mph. It is manual transmission. So, I can list the following:

1) Knocking is audible when cruising steadily with gentle gas pedal and disappears when heavy acceleration.
2) knocking disapears when I depress clutch to disengage transmission.
3) no knocking when I accelerate aggresively.
4) knocking dissapears when I am cruising and depress clutch to disengage transmission.
5) when reach a velocity of about 55 mph and decide to coast to a red light I depress clutch , shift to neutral and knocking disappears.

Gotta be the MT, right? What can it be? I dont think it is a danger for driving, right?


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## Texican57 (11 mo ago)

throw out bearing?


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## Thom Paine (Nov 24, 2021)

MT ???


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## papereater (Sep 16, 2016)

Texican57 said:


> throw out bearing?


Put it in new when I replaced the clutch. But one never knows, could be a defect.


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## chandler48 (Jun 5, 2017)

High gear missing a tooth or two. I have that effect on my 1955 Ford 640 tractor in second gear.


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## papereater (Sep 16, 2016)

Thom Paine said:


> MT ???


Manual Transmission (as opposed to an AT).


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## papereater (Sep 16, 2016)

chandler48 said:


> High gear missing a tooth or two. I have that effect on my 1955 Ford 640 tractor in second gear.
> [/QUOT
> 
> Wow, good to know someone else has seen this. But what made your determine it is a tooth? Can we really compare a tractor to a road vehicle doing 50-60 mph with same knocking? I drove a tractor once pulling logs out of a forest and there is much noise, not sure one can even notice that. But your experience is useful.
> ...


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## Thom Paine (Nov 24, 2021)

papereater said:


> Manual Transmission (as opposed to an AT).



You're positive the noise is coming from the transmixer, eh ?


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## raylo32 (Nov 25, 2006)

If the only thing different between before the work and now was the clutch job... and since the noise goes away with the clutch disengaged.... it is likely the clutch or a component like the throw out bearing. Could be just about anything. Maybe a loose rivet or something on the pressure plate or friction disc. Sad to say, you are going to have to take it all apart again. I doubt the chipped gear tooth, unless there was some sort of event that might have caused that. Are you out there in the wee hours street racing the old Sunbird? ;-) If the clutch looks OK you would have the tranny out so then have a look inside there.


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## chandler48 (Jun 5, 2017)

Both tractor and car will exhibit similar "clicking" sounds with a tooth missing on a particular gear under pressure. As you said, once the clutch is disengaged the noise quit.


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## Thom Paine (Nov 24, 2021)

raylo32 said:


> If the only thing different between before the work and now was the clutch job... and since the noise goes away with the clutch disengaged.... it is likely the clutch or a component like the throw out bearing. Could be just about anything. Maybe a loose rivet or something on the pressure plate or friction disc. Sad to say, you are going to have to take it all apart again. I doubt the chipped gear tooth, unless there was some sort of event that might have caused that. Are you out there in the wee hours street racing the old Sunbird? ;-) If the clutch looks OK you would have the tranny out so then have a look inside there.


My thoughts also lean toward the pressure plate... if it's in the tranny area.


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## papereater (Sep 16, 2016)

raylo32 said:


> If the only thing different between before the work and now was the clutch job... and since the noise goes away with the clutch disengaged.... it is likely the clutch or a component like the throw out bearing. Could be just about anything. Maybe a loose rivet or something on the pressure plate or friction disc. Sad to say, you are going to have to take it all apart again. I doubt the chipped gear tooth, unless there was some sort of event that might have caused that. Are you out there in the wee hours street racing the old Sunbird? ;-) If the clutch looks OK you would have the tranny out so then have a look inside there.


LOL, if I was a crazy street racer my Sunbird would have been in the junk yard years ago. I baby my car, orig clutch lasted to about 215,000 miles. 

Id hate to take it apart again, wow, so much work. I did use blue loctite on the bolts for the pressure plate. I might have to live with this for a while, hoping it does not get worse.


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## lenaitch (Feb 10, 2014)

To me, 8 to ten times per second is a buzz not a knock.


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## huesmann (Aug 18, 2011)

You replaced the pilot bearing too?


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## papereater (Sep 16, 2016)

huesmann said:


> You replaced the pilot bearing too?


Best I could determine at that time there is no pilot bearing. At least, Rock Auto clutch kit does not include it (even though I ended up returning it because it was the wrong size clutch). I thought it was strange, no pilot bearing. But if no pilot bearing, what is there? Just a raw hole?


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## papereater (Sep 16, 2016)

lenaitch said:


> To me, 8 to ten times per second is a buzz not a knock.


No buzzzzzzzz, knock/knock/knock. 10 times /sec, dependent on the cars velocity.


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## Oso954 (Jun 23, 2012)

papereater said:


> Best I could determine at that time there is no pilot bearing. At least, Rock Auto clutch kit does not include it


The pilot bearing is not a clutch part, it’s a fly wheel part. The pilot bearing is mounted in the center of the flywheel and supports the front end of the transmission input shaft.

I’ve done a lot of clutch work (although it’s been a while). I don’t recall ever getting a pilot bearing as part of a clutch kit. You requested them separately. If you didn’t, a good parts guy would probably ask or suggest you get one.


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## chandler48 (Jun 5, 2017)

May not be the case with your speed racer, but I found out on my Ram 3500, the pivot ball is very vulnerable to wear. It is nylon for some unearthly reason  and sees a lot of motion. Some vehicles have it and some don't.


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## raylo32 (Nov 25, 2006)

Some cars have pilot bushings instead of bearings. But you certainly have something. Regardless of the type these are generally replaced when you do the clutch.


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## huesmann (Aug 18, 2011)

Oso954 said:


> The pilot bearing is not a clutch part, it’s a fly wheel part. The pilot bearing is mounted in the center of the flywheel and supports the front end of the transmission input shaft.
> 
> I’ve done a lot of clutch work (although it’s been a while). I don’t recall ever getting a pilot bearing as part of a clutch kit. You requested them separately. If you didn’t, a good parts guy would probably ask or suggest you get one.


The clutch kits I've bought have always included a pilot bearing and throwout bearing, plus an alignment tool. Now, you may or may not want a better quality bearing than what's included, but that's a separate issue. (These clutches have been on Mustangs, Corvettes, Miatas.)


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## Brainbucket (Mar 30, 2015)

Sure it's not a u-joint?


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## lenaitch (Feb 10, 2014)

.....


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## papereater (Sep 16, 2016)

Thanks, people.


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## papereater (Sep 16, 2016)

Wait! What if its the transaxle, the cv joints in the axle I just put in new when I did the clutch job? It is from AZ, lifetime. I could do the test, put in reverse and pump the gas, and see/listen if I Hear a click-click click. Will try it tomorrow. I hope that's it and not the pilot bushing or broken tooth. 

When driving, the noise could be from that area.


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## HotRodx10 (Aug 24, 2017)

papereater said:


> Wait! What if its the transaxle, the cv joints in the axle I just put in new when I did the clutch job?


Could easily be a bad CV joint. I had a brand new one that was bad, once.


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## papereater (Sep 16, 2016)

Figured Id post what happened- turned out that noise which started as suspect transmission disappeared. How? Have no idea, but meanwhile I ended up finding out my front strut was shot, so put in a new one. Also, tie rod end was bad, so put in a new one. No more noise. 

What looked like a signature transmission related racket never was, apparently. Life can be full of surprises. My 35 year old car lives on, as a daily driver. Anyway, thanks to all here who offered advice/help when I needed it.


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## Nealtw (Jun 22, 2017)

Was the flywheel removed when the clutch was changed, it could be loose.


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## papereater (Sep 16, 2016)

Nealtw said:


> Was the flywheel removed when the clutch was changed, it could be loose.


Flywheel was removed, and resurfaced by a local pro machinist. I tightened it down to torque specs, WITH blue threadlock. But Neal, I explained that the tranny noise is gone. Thats a good thing, right.....LOL!


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