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New clutch...Noise when clutch is not depressed and trans in N?

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After I installed a new clutch on my L28 w 5 speed I have some noise that I can only assume is the throwout bearing. Could be wrong though. When the clutch is pushed in theres no noise but when the clutch is out and trans in N there is a noise from the clutch area. Any thoughts? I know about the throwout bearing collars being diff sizes but I think I have the correct one. Could I have misaligned the clutch installing it?

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One of the bearings in the transmission is known for making noise.  I think it's the countershaft bearing.  Doesn't hurt anything it's just annoying.  There are stories of replacing the bearing with a new one and have ing the nosie come back within a very short time.  Might be why Nissan went to a bigger bearing with the 71C transmission.

What kind of "some noise" is it?

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My '77 does the same, whinning spinning noise until I push the clutch pedal down.

Zed Head knows way more than me on these cars especially transmissions.

I can say this from my personal experience. I drove the throwout bearing on using the old one as I had read online. I had the throwout bearing pressed on the collar at a machine shop on my 240. No noise, same clutch kit. Just putting that out as more info.

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I take it that L28 is in a 280Z. Did you do anything to the slave cylinder? Change it for another unit?

Reason for asking. The 280Z slave cylinder has a spring behind the piston. It has two functions: 1. Prevent free play in the mechanicals between slave clinder and throwout bearing. 2. Keep the throwout bearing on the pressure plate so it spins with the pressure plate and doesn't slip. If it slips, it generally squeals or makes a peeping noise that comes and goes.

It is easy to test. The noise will disappear if you apply the clutch a little.

 

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I would say it sounds like a bearing noise. It's not very loud it could in my mind be the throwout bearing and pressure plate not contacting properly.

The slave is a older non internal spring adjustable. It has a tab for a spring. I installed a spring but it does not quite the noise. Nor does holding the clutch fork back fully remedy the noise.

The noise goes away with clutch depressed. 

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It's quite odd that, presumably, the sound was not present before the new bits went in.

There's no chance it's clutch misalignment.  The disc is the only component that could be misaligned, and if it were, you'd never get the trans back in.  And even if you were to get the trans reinstalled with a misaligned disc, as soon as you depressed the clutch pedal, the disc would be freed to center itself.

Noises are the hardest to describe.  If the release bearing were in light contact with the pressure plate, it would be making some sound - audible or otherwise. Depressing the clutch would load the bearing past its light load, incidental contact condition and either make it sing or reduce its sound level. 

Try readjusting the throw on the master cylinder to ensure ample clearance (free-play) in the pedal. 

It is possible that the parts you received are not correct (can you say misboxed?).  It's happened to me.

Are you certain the clutch release lever is properly seated on the pivot post, and the lever has freedom to move?

Be certain there's no residual pressure on the clutch slave.  Cracking the bleeder will let you know - if brake fluid blows out, not passively drips out, then you had some force acting on the release lever.

Well that's  it.  I'm in the middle of cocktail hour!??

 

 

 

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This has the classic signs of noticing something that has always been there because you just did some work in that area.  I had three different five speeds in my car that all made the bearing noise.  Different sleeves, pressure plates, etc. but they all sounded about the same.  Pedal down, noise gone; pedal up, noise there.

Drive it for a few days and see if it changes.  It will probably get a little louder when the oil is hotter and thinner.

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My 72 with 79 280Z five speed makes the same noise.  Clutch out, noise.  Depress clutch, noise gone.  All new clutch components.  As others have said, my assumption is that it is not the throwout bearing as there is no load on the bearing when the clutch is out and the noise is present.  If I depress the clutch slightly, the noise stops.  So, I guess it could be throwout bearing slop/end play at work.

But, the noise certainly sounds like bearing noise which I assume was the input shaft.  I'm living with it....

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DavidF: That's the part I'm having trouble with.  If the pressure plate and release bearing are lightly loaded, the noise stops.  I am assuming "slightly" doesn't begin to release the clutch.  If I'm wrong, skip the rest ?

So the clutch disc is still coupled to the flywheel and spinning at engine rpm. 

The release bearing is now spinning at or near engine rpm. 

The torque on the transmission input shaft, if any, hasn't changed and neither has its rpm. 

The crankshaft has some axial reaction force loading it toward the front of the motor.

The clutch release lever is loaded to eliminate any free play.

I think that's everything that's going on. 

What of these, or others missed, acts on the input shaft bearing to change its loading?  Before I start assembling my car, I plan to rebuild the trans (same one as yours David F) and it'll get new bearings, but I'd really like to know if maybe something else is also contributing to the noise problem so I can fix it now.

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Posted (edited)

only thing diff between N and all the other gears engaged is the output shaft not coupled to any of the syncro hubs. So all the gears as spinning around on needle bearings, the counter shaft and input shaft are spinning on ball bearings, lots of action but for the turning of the output shaft (2 ball bearings not engaged). My guess is its just normal noise that is masked by lots of other noises that are there in any other gear. It really is a matter of degree of loudness as to whether there is a real problem or not. You can do a pretty good inspection of the gears once the case is split, and the forward counter shaft bearing (the small one) is not too hard to remove and replace if you suspect it. The main adapter plate is a LOT more involved, I would look for signs of actual failure or excessive radial play before diving into those bearings. Don't get me wrong its actually kind of fun to work on them, just saying you could end up doing a lot of work just to find out its still going to make some noise.

Edited by Dave WM

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Posted (edited)

Did you replace the throw out bearing or is it the original? Did you check if it turned freely before fitting the transmission? What you are describing sounds like a noisy throw out bearing.

If it is what I think it is, you will know soon enough when you take it for a test drive.

It will make the noise when you are driving it in all gears. If you depress the clutch pedal slightly and the noise goes away. It's the throw out bearing.

Edited by EuroDat

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1 hour ago, Dave WM said:

The main adapter plate is a LOT more involved, I would look for signs of actual failure or excessive radial play before diving into those bearings. Don't get me wrong its actually kind of fun to work on them, just saying you could end up doing a lot of work just to find out its still going to make some noise.

Thanks for the insight.  What we need is a way to test a bearing that's better than the give it a quick flick and listen test, or spin it to feel for roughness.  These techniques work fairly well after you've gotten some experience, but it's not a reliable method, especially since you can't vary the load.   As you mentioned, there are several bearings operating, and any one or more could combine to sing under certain conditions.  Of course, there's always the shotgun approach - change 'em all!

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 I always used the shotgun approach on transmissions. Along with all new bearings, all new seals, all new synchros and check the prop shaft u-joints while it's out.

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Learn to enjoy the noises(s).  As soon as you remove one you'll notice another.  Coming up: diff howl, 3rd gear whine, rocker ticking, injector noise, mustache bar clunking.

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Does it run? Be happy!

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19 hours ago, Mark Maras said:

 I always used the shotgun approach on transmissions. Along with all new bearings, all new seals, all new synchros and check the prop shaft u-joints while it's out.

What was the most commonly reported need for the rebuild(s)?

Were you ever able to do a before and after comparison?

 

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18 hours ago, Zed Head said:

Learn to enjoy the noises(s).  As soon as you remove one you'll notice another.  Coming up: diff howl, 3rd gear whine, rocker ticking, injector noise, mustache bar clunking.

Yeah, I'm with you completely.  Valve train sounds (aot noise) have always bugged me, other not so much.  A good stereo drowning out those annoyances isn't masking, it's enhancing the user experience.

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I do not understand the comments about the throw out bearing being the cause of the noise. When the clutch is out (i.e. not depressed) there is no load on the TO bearing.  When you depress the clutch, the TO bearing comes into play.  So, saying the TO bearing is making the noise in neutral makes no sense to me.  My TO bearing is brand new and noise there from day one.  Seems like transmission bearing noise to me.

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Posted (edited)

EuroDat explained it in the post below.  There's a spring inside the 280Z style slave cylinder that takes up all of the play at the clutch fork.  It can't apply much force, it's a small spring, but it is there and it does work.  If I was checking that theory out I'd crawl or reach under the car with the engine running and move the fork away from the pressure plate by hand.  You can reach it from the engine bay also.  You might have to have someone sit in the car to listen since the noise is amplified in the cabin.

Here's the FSM drawing.  I put a red dot under one of the spring coils.

image.png

 

Edited by Zed Head

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Posted (edited)
16 hours ago, ETI4K said:

What was the most commonly reported need for the rebuild(s)?

Were you ever able to do a before and after comparison?

 

 The first two refreshes were for a serious grind going from first to second and a a mild grind going from second to third. Two others were bearing noise only. Complete success on all of them. Here's a thought. The first trans Was for the snick when changing gears. The synchros I removed looked near pristine. I reused them later in another trans. The shotgun refresh fixed the original problem but when I used the old synchros (near pristine) in a later refresh they too fixed the shifting problem. WTF, said I. Skip to years later when there was a discussion here about gear oil. Some brands work much better, shifting wise and I'm assuming  it could affect bearing noise too. I wonder if a gear oil change would improve things? @Zup highly recommends A/C Delco Friction Modified. I now wonder if my first trans with the shifting problem had really been fixed with a different gear oil. Back then I probably used a Kendall product.

Edited by Mark Maras
Old age.

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