1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

New clutch/ gearbox noise

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Old Aug 23, 2003 | 08:07 AM
  #1  
djmickyg's Avatar
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From: Australia, Melbourne
New clutch/ gearbox noise

To go along with my noisy thrust baring i have a new noise..
its ocming from the clutch area it sorta sounds like a very mild grinding noise (not like when the diff chewing up spider gears) and it goes away as soon as i press the clutch, which is why i think its the gear box.. the oil in the gear box was changed at the start of the year. could it be time for some new oil.

its still changing gears very easily like it was a year ago.

what could this be?
thanks
Mick
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Old Mar 1, 2005 | 09:32 PM
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From: virginia
im bringing this back just because i didnt wanna maker a new thread after i searched

i have this same noise its comming from the cluster cause in 1235r it makes a noise but 4th is quiet

is this normal or what
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Old Mar 1, 2005 | 10:26 PM
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Djmickyg - what you describe is likely the Throw-Out Bearing (TOB), this bearing rides against the clutch disk 'fingers' and presses the clutch disk against the flywheel and cover plate. The TOB should always be replaced with the clutch, just because it's a $15 part that's right there when you're doing the job.

My diagnosis on this is due to your statement about it going away when you press on the clutch, thus disengaging it from the spinning engine and stopping the noise. When you let the clutch out in neutral, the clutch (and tranny gears) spin with the engine and the TOB spins as well.

If you stated that the noise went away when you RELEASED the clutch, it would be your Pilot Bearing. The Pilot Bearing keeps the transmission input shaft centered in the flywheel and mounts the clutch. When your PB goes out, it usually grinds like gears going, but as soon as you let your clutch out, it goes silent.

Hope this helps, and reply back if you're looking for more information,
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Old Mar 1, 2005 | 10:51 PM
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From: Lynchburg, VA
renagade_rotary,

Check out this page: http://www.mazdatrix.com/g2.htm

It sounds like you probably have a bad bearing in the transmission. The only way to fix is to rebuild/replace the transmission. You may be able to get by awhile yet. Try to replace the old gear oil with some good synthetic gear oil. This may help alleviate the problem for now.

Kent
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Old Mar 2, 2005 | 06:09 AM
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In my experience with transmissions and general noise issues, I've had bad input shaft bearings which got really vocal and the noise came from the front of the transmission. A bad throwout bearing would be noisy when you press the clutch pedal not when you release it. When the clutch pedal is up, the throwout bearing is out of the way. When the pedal is down, the bearing is pressed up against the pressure plate diaphragm and hence loaded up which causes the ***** in the bearing to ride hard agains a worn race.

This sounds like a bad input shaft bearing and I've had a few RX7s with that problem. If the noise diminishes when you press the clutch in, it's because the loading changes on the bearing.

The pilot bearing is a thin needle bearing - believe me, you won't hear that noise, it will just disintegrate if it seizes up. The input shaft is always engaged with the pilot bearing. The worst I've had with a pilot bearing is that the needles jammed against the input shaft causing the transmission to be constantly engaged with a spinning engine - nasty experience since it came and went and it usually came at the worst time, like cranking the engine to fire it up and the car lunged forward - I almost hit someone one time.

My opinion is that it's a bad transmission bearing, not the throwout bearing or pilot bearing.
Redline oil has worked wonders for me in terms of noise reduction and even synchro issues. These transmissions are fairly easy to rebuild - take it out and rebuilt it. It's always fun!!
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