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Discussion Starter #1
Hello guys, I need your help. I have swapped ZC 3rd and 4th gears in my S8G gearbox (late del sol). Modification was done to the mainshaft 4th gear as seen in this forum, it was straight forward and easy. After assembling the gearbox, everything seems to work but I here a strange noise, especially when I press the clutch and car is moving (mainly with first gear but sound is also audible (less) with 2nd or 3rd engaged). It sounds like reverse is trying to engage.

I drove about 50 miles and decided to open the gearbox again. Problem is that nothing strange or destroyed was found! No metal debris, nothing. So decided to measure some clearances and reassembled the gearbox.

Sound is still there. I have driven an additional 150 miles and I am thinking to open gearbox again see if everything can now be seen and get a synchrotech rebuild kit with carbon synchros and new bearings.

Any ideas on what might have gone wrong?
 

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Discussion Starter #3
When reverse is engaged and car is moving, the sound is different as reverse is straight cut, not helical. Well, something like this is heard from my tranny but only in the conditions I mentioned above (especially when clutch pedal is pressed and either neutral, 1st, 2nd and 3rd is engaged). I cannot really describe it more, English is not my native language and it is a little hard to describe noises. I will open up the gearbox again probably late next week and see.
 

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1996 Civic Type DX
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If the car is not moving, clutch is disengaged and the trans is in gear with the engine running, there should be no change in sound as the trans being in gear doesn't affect anything as it isn't spinning. If it makes a noise under the same conditions but the car is moving, it will make a whine when the transmission is spinning faster than it normally would (i.e. its in first gear with the clutch disengaged and car moving at 50mph).
 

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Discussion Starter #5 (Edited)
It only makes a sound when car is moving, clutch is pressed but not without the limits of an otherwise 'normal' rotation speed. For example you put 1st you accelerate to 10mph and you press the clutch to change to second gear. The time you press the clutch, you hear this sould from the gearbox. It sounds like reverse idler gear is messing with a gear or sth at that point. However I also suspect a bearing or incorrect shaft shimming (although shimming should not change as I am using the same transmission housing with the same shafts).
 

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May not be the problem but I had the reverse sound in most gears once it turned out to be the throw out bearing fork had broke on one side and it was hard to get out of 5th gear also.
 

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Discussion Starter #8
Would you ever suspect a needle bearing inside gears? I have never seen them fail but who knows. I got a rebuild kit to be fitted this week but it does not contain needle bearings.

Btw, I am supposed to use the zc 3rd needle bearing as everyone suggests and this is what I initially did. but when I reassembled the shafts to see what this sound was, I noticed that since it is shorter than hydro 3rd, there would be excessive play. So I used the longer (hydro 3rd) needle bearing. Nothing changed though so it was not the reason. But since I am rebuilding this week, should I finally use the short or the long needle? It does not seem to make a difference anyway.
 

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Discussion Starter #10
And you can tell if they fail? If they look fine, is there a chance they have failed and produce noise? Also Aquafina, have you ever assembled a D hydro gearbox with ZC gears? What needle bearing you use for the 3rd? The ZC short one or the cable longer one?
 

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Brokedick Millionaire
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I used the stock rollers under the ZC gears in a 92-00 box. I have seen them fail but it was generally due to ran low on oil or the oil ports were clogged, and they seized up. But themselves didn't fail.
 

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When they fail you can tell by looking at them, they come apart in pieces. I've built many hydro transmissions with ZC gears. Use the stock needle bearings.
 

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Discussion Starter #13
When you say stock, you mean the stock hydro ones, right? Thanks guys, my rebuild kit just arrived so I hope I find some time till the end of the week to open it up and see what is wrong.
 

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Discussion Starter #15
I am frustrated. Changed all 7 bearings and nothing changed. There is no debris caught on the magnet and I could not locate wear anywhere inside the gearbox. Tranny itself works like a champ but I get a strange noise when 'load direction' changes. More specifically:
1. No noise when accelerating (or can't hear it)
2. Very little (if any) noise when decelarating with gears engaged
3. Noise is heard mainly if you accelerate with 1st gear and then depress clutch with 1st gear still engaged so now power is transferred from the secondary to the mainshaft.
4. Noise is much less using the same procedure as in (3) with the rest of the gears and becomes quite audible again with 5th (still less than 1st). What changes in fifth gear with clutch depressed is that the sound is not continuous but intermittent (comes-goes, following the frequency of rotation).

In the following video, I accelerate slightly with 1st gear and depress the clutch in second 4. You can then hear the strange sound then. Any ideas?

https://youtu.be/AgTDj7214SU

Specs:
S8G del sol '96 gearbox
ZC 3rd and 4th gears
0.771 5th from euro spec civic 92-95 d16z6 powered gearbox (shorter than US EX)
Mfactory helical LSD (thrust clearance set correctly)
All brand new bearings

Sound started when I swapped to ZC gears. I have carefully modified the ZC 4th and measured every possible dimension of it. I made it identical to hydro 4th. Could this sound be a bad 1-2 syncro-sleeve-hub set? The only thing I have not done is measure primary shaft thrust clearance as I do not have all the equipment. But tranny was working perfectly and dimensions of ZC gears were REALLY close to the hydro parts I replaced so thrust should not change.
 

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Discussion Starter #17
You are right. Any thoughts on this issue? I am leaning towards 1-2 hub-sleeve and/or some needle bearing failing allowing gears to go out of alignment. This time, I did not disassembled the shafts, just replaced all bearings so I could not check needle bearings.
 

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Discussion Starter #18
By the way, do you have to flip the hydro 3-4 hub when using ZC gears? I did not do anything like that.
 

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Brokedick Millionaire
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Figure out which gear it doesn't make the noise while car is on jack stands, likely the roller bearing for that gear.

You tore the trans down and apart, but didn't check them, but those in a new bearing kit and the noise is still there.
 
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