Knocking from clutch/tranny area in neutral... (1 Viewer)

[Jesper]

So i put a new clutch/throwout bearing in about 4 months ago, followed the many write-ups and all went well..sounded good, felt good, no issues.

About a week ago I started noticing a knocking sound from under the stick shift any time I would get to a red light and put it in neutral. As soon as I depress the clutch pedal, even partially, it goes away. I took the inspection cover off and looked around, nothing obviously loose or disconnected. The clutch/flywheel area looks dry and clean. There is some dampness/oil that seems to be coming down the shaft from the front of the tranny (input shaft?).

Watching everything move while the engine runs, I can clearly hear the knocking sound from somewhere right in there but can't figure out if it's in front of the shift fork or behind. As soon as the clutch is depressed and the fork puts any pressure on the clutch the knocking goes away.

Any input on how to further diagnose without spending 2 more days disassembling everything? I feel like I could replace a throwout bearing if needed but don't want to tear everything apart to find out the problem is within the tranny, which I'm not comfortable breaking open and trying to figure out.

Thanks.

 

[mongoose2231]

I'd say do this. Get under there and see if there's any play between the fork and the slave rod. Mine does the noise too but it's because I adjusted my clutch pedal to make sure the clutch fully engages. My clutch, even though brand new, grabs in the last 1" of the pedal stroke. Maybe wrong master by po as that seems to have been replaced at some point, long story short is i know I have some tiny amount of play between the fork and the slave rod, and it makes a ruckus in there while in neutral and such.

 

[Output Shaft]

The transmission is not the problem, it's the messenger. That clanking often is caused by a non-smooth idling engine shaking the gears.

Check the compression in all the cylinders. A single low cylinder can cause tranny clank.
Give the engine a tune up.
Ensure that all spark plugs are firing.
Set the idle speed at 700 rpm or a tad higher.
Check to ensure that the Hot Idle Compensation valve in the air cleaner is hooked up correctly and functioning as it should.

 

[HemiAlex]

The transmission is not the problem, it's the messenger. That clanking often is caused by a non-smooth idling engine shaking the gears.

Check the compression in all the cylinders. A single low cylinder can cause tranny clank.
Give the engine a tune up.
Ensure that all spark plugs are firing.
Set the idle speed at 700 rpm or a tad higher.
Check to ensure that the Hot Idle Compensation valve in the air cleaner is hooked up correctly and functioning as it should.

That was completely my issue. Fred called it for me. I had the same symptoms EXACTLY. I refreshed the top end to eliminate the 25psi cylinder and the knocking stopped.

 

[Jesper]

Thanks much. Idle has been a bit rough. I'll check compression/plugs/idle today and go from there.

 

[Jesper]

Compression is good on all cylinders - 130 lowest to 150 highest.
Spark plugs had been gapped slightly larger than spec., about .038" and starting to look whitish.
I put in new plugs set to the correct gap. Looks like my mixture may be a little lean and perhaps exacerbated by a phantom vacuum leak somewhere.
Going to reset the valves, fiddle with the mixture and start tracing vacuum lines again. Can't hurt - still eyeballing the clutch fork/bearing/input shaft area.