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09 RX8 Transmission Occasional Grinding

Old 06-25-2012, 10:44 PM
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09 RX8 Transmission Occasional Grinding

Been reading some threads on here. I am not too mechanically advanced so perhaps people can help me diagnose the issue.

I got a used 09 rx8. After some time mazda replaced my transmission with a brand new unit under warranty because of bad grinding issues (it took just one drive with the service manager for them to agree). At the same time I put in a brand new clutch just in case (there was no need).

I followed proper break-in procedure, kept the oem fluids for around 1.5k and then put in redline fluids into the tranny and diff.

I generally baby the transmission - double clutch, heel and toe, breath the shifter into position, etc. Left foot is always on the dead pedal when not shifting, no drag racing or clutch dropping. Driven manuals for most of my life.

About 10k have passed and I started noticing some issues. It seems that the engagement point shifted higher. On occasion the transmission stared grinding with the clutch fully depressed.

Once, while moving in slow traffic (2mph) with the clutch fully depressed there was grinding going into gear (I think I was going into 1st).

On another occasion there was grinding going from 5th-4th-3rd again with the clutch fully depressed heel and toeing from about 80mph to 40 mph - 3rd gear grind.

It feels like "something" is not engaging/disengaging immediately. Almost as if there some part that is not responding fast enough.

The clutch itself also feel more violent with respect to the bite than the older one (although that is probably normal).

I read the series II transmission is supposed to be fairly reliable so I can't believe there is another issue with the unit I got from Mazda.

Any thoughts on what the culprit could be? Any additional tests I can do? Before I take it to the dealer?

Thanks for your help!!!
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Old 06-26-2012, 04:18 AM
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Hello and welcome..

First what is the total KMS/Miles of your Series 2 RX-8, If you can PM me your VIN Number I can look up a few details which could also answer some of your questions.

You are in the USA?

US is generally the only country which replaces complete 6 Speed Transmissions, others just renew the 5-6 Synchro Ring and Hub, which is all that has basically changed for Series 2 P66M Transmissions between 2009 and 2012.

There is a possibility if Left Hand Drive that you could have the earlier Clutch Pedal Bracket which has a few problems in Series 1's.

A new "clutch" should not be an issue as they are all the same Genuine, the Thrust Bearing did change from Series 1 to Series 2, apart from that the Clutch and Pressure Plate are the same.

Again PM me your VIN and I can help you a lot more, give you some more ammunition before you go to a dealer, there is an extended warranty on Clutch Pedal Brackets "IF" you car is within a certain VIN Number .

Does your Clutch Pedal squeak, or look out of shape /alignment when compared to your resting Brake Pedal?
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Old 06-26-2012, 09:24 PM
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Originally Posted by ASH8 View Post
Hello and welcome..

First what is the total KMS/Miles of your Series 2 RX-8, If you can PM me your VIN Number I can look up a few details which could also answer some of your questions.

You are in the USA?

US is generally the only country which replaces complete 6 Speed Transmissions, others just renew the 5-6 Synchro Ring and Hub, which is all that has basically changed for Series 2 P66M Transmissions between 2009 and 2012.

There is a possibility if Left Hand Drive that you could have the earlier Clutch Pedal Bracket which has a few problems in Series 1's.

A new "clutch" should not be an issue as they are all the same Genuine, the Thrust Bearing did change from Series 1 to Series 2, apart from that the Clutch and Pressure Plate are the same.

Again PM me your VIN and I can help you a lot more, give you some more ammunition before you go to a dealer, there is an extended warranty on Clutch Pedal Brackets "IF" you car is within a certain VIN Number .

Does your Clutch Pedal squeak, or look out of shape /alignment when compared to your resting Brake Pedal?
Thank you ASH8.

I have 100k on the car. The clutch pedal appears to be in alignment with the rest of the pedals.

One thing I noticed is that when I start the car in the garage and play around with the clutch pedal (without selecting any gears) the rpms are effected - they jump up and down based on the release of the clutch (not sure if this is normal for this car).

What I find strange about the grinding is that it is occasional. Previously when the gears started grinding things got progressively worse and never went away until the transmission was replaced.

I am sending you a PM with the VIN.
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Old 06-26-2012, 09:59 PM
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Putting foot up/down on the clutch pedal and noticing a 'slight' difference in RPM is not something I would consider an issue, all stick cars will show some change as you are releasing clutch plate and therefore engine load through to the input shaft and trans while in neutral, so clutch out revs lower, clutch in (to floor) revs higher.

OK, your VIN tells me you have the older/earlier Clutch Pedal (same as Series 1).

So you will have the extended warranty for this 'IF' Clutch Pedal fails,
trouble is Warranty is 8 years or 100K mikes, BUT your mileage is out, no warranty for your Clutch Pedal Bracket.

https://www.rx8club.com/showpost.php...9&postcount=11

You have already had trans replaced so you should already have the latest unit.
Frankly, I think your occasional grinding could be related to changing too fast, or slam changing, or pedal timing/changing issue?

Not suggesting you do, but from me right now, if you don't want to go to a Mazda Dealer, I suggest you find a local Mazda RX-8 club member who can/will take your 8 for a drive and have a look and compare.

Sadly you are not going to get anything much from Mazda as you are now over 100K miles.
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Old 06-26-2012, 10:30 PM
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Thanks ASH.

If I did not experience grinding with the clutch fully depressed and while barely rolling there would be some merit to the shifting too fast etc (which I never do).

I will look into the clutch pedal to see if it was replaced.

Thank you for your help.
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Old 06-27-2012, 02:15 PM
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I would be getting the Clutch Bracket looked at for any cracking or movement, see the Series 1 section for that one.

Considering your mileage and use, I would also look at your clutch hydraulics, there has been some Slave Cylinders leak or give out (all RX-8's use the same parts) and even the Clutch Master-cylinder....the easiest way to really check the condition of this one is to get the Slave Cylinder bleed (bled) and look at the fluid you might find a silver looking gunk (alloy) in there, or it could be clean and at the very least you may remove any air that could be in the clutch fluid lines.

The end result will be a better Clutch Pedal feel and use.

If so replacement usually of SC is necessary.
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Old 06-28-2012, 04:34 PM
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I was gonna say the clutch pedal bracket might be the issue. S2 still has very flimsy clutch pedal.
mine seems moved.
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Old 07-09-2012, 04:32 PM
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My clutch felt like an on/off switch until I put about 15,000 miles on it.

Don't baby the transmission. Shift precisely, but shift quickly and forcefully too. The transmission is designed to work well when the car is being driven hard; the synchronizers won't work right if you try to apply the least possible force while shifting.

You can test that the synchronizers are working right by attempting to shift while the engine is idling, the car is stopped, and the clutch is closed. The synchronizers should all resist shifting even with substantial pressure applied to the shift lever. If one or more gears try to engage when the clutch is closed, you can burnish the synchronizer to improve its performance by lightly pressing the shift lever for a couple seconds, releasing, and trying again. When all the synchronizers resist substantial pressure on the shifter, you're done. You may have to repeat the burnishing procedure occasionally, but it's not a huge effort; you can do it at a stoplight.
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Old 07-12-2012, 11:51 AM
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I would have to agree with fyrstormer - after having the R3 for just 2 months, I've been noticing the engagement is strictly depepndant on the force used while driving. It seems to shift rough/grind during slow shifting.
I'm actually determined to find out the material which the synchro blocker ring in this specific trans is made out of.. maybe a harder material compared to brass which is more commonly used... if so, there may be longer speed matching between the idler gear and mainshaft which can cause grinding..
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Old 07-12-2012, 11:56 AM
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My understanding is the blocker rings are made of a steel backing with a carbon composite friction surface bonded to them.

Grinding isn't caused by the synchronizer taking a long time to complete synchronization; as long as the synchronizer is working properly, it will simply prevent the shifter from completing the shift until the input and output shafts' rotational speeds are synchronized. Grinding is caused by a broken blocker ring, or insufficient friction between the blocker ring and the side of the gear; both of those scenarios cause the blocker ring to fail to prevent the lockring from trying to mesh with the splines on the side of the gear.

In the case of this transmission, the synchronizers seem to have unusually stiff return-springs attached to the blocker rings, so the driver has to shift more firmly to apply enough friction between the synchronizer and the gear to make the blocker ring work properly.

Last edited by fyrstormer; 07-12-2012 at 01:02 PM.
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Old 07-12-2012, 12:41 PM
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Correct. Which is why I'm curious of the exact material of the ring used in this transmission.

Steel backing with carbon comp seems quite hard/brittle for the ring (which explains premature failure), unless this is the current mat'l being used instead of brass in today's gearboxes..?
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Old 07-12-2012, 12:59 PM
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My dealer explained to me that the "carbon triple-cone synchronizers" were used because they don't wear down as fast under the higher stress of fast-shifting a gearbox connected to a 9000rpm engine.

It sounds like a reasonable explanation. Brass is pretty soft compared to most metals used for load-bearing tasks, and the primary reason it's used for synchro cones in most gearboxes is because it won't gouge the friction surfaces on the gears.
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Old 07-12-2012, 02:32 PM
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Knowledgeable dealer! That seems likely, and good point bringing up the engine-rev capabilities since it has alot to do with the design of the gearbox.
Thanks for the info!
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Old 07-13-2012, 11:39 AM
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I too have the grinding 5th gear problem,which is being sorted out at the Dealers next week under Warranty

My R3 is a 2009 model with just over 17,000 miles on the clock
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Old 07-13-2012, 03:56 PM
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interesting. mines shifting perfect at 22000 miles. the only time I would grind it is when I let out clutch too fast meaning half way through the shift. usually happens on upshift, where the clutch is let out and gas is applied before the gear is completely in.
but thats only when my seat is not adjusted properly meaning clutch is not all the way to the floor.
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Old 07-13-2012, 07:24 PM
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Could not agree more Jason..

For the record...I must be living on a different planet, with both my P66M trans 'force when changing' is not needed, sure when cold 2nd can be a bit of a pain, I just drop it in @ slower speed/rpm, once warmed up a little it is fine.

I will bet my (you know), that Synchro's are brass, the Carbon 'coating' wears off, it has to be a softer metal (brass), every ring I used to sell in Mazda's gearboxes were/are brass.

I could be wrong with current Trans, but I doubt it.

There is a reason 'why' a GL4 oil has to be used in your Trans.

Here is what Redline says about their MT90.

75W90 GL-4 gear oil (similar to SAE 5W40/10W40 engine oil viscosity)
Popular in Nissan, Mazda, Mitsubishi, VW/Audi, Lotus Elise/Exige, Toyota
Offers quicker shifts, perfect synchronizer coefficient of friction
Safe for brass synchros, as it lacks the reactive sulfurs found in most GL-5 oils that cause damage
High performance gear protection and longer synchro life
Eliminates notchy shifting, even when cold
Satisifies the gear oil viscosity requirements of 75W, 80W and motor oil viscosities of SAE 40, 10W40, and 15W40
Recommended for GL-1, GL-3, and GL-4 applications, as well as where most special synchromesh fluids are specified


http://www.redlineoil.com/product.aspx?pid=46&pcid=7
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Old 11-24-2015, 08:41 PM
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Hello guys! I just got my 8 and I'm curious about something - when it's cold, is 2nd gear normally kind of a pain to get into? And, if so, why? I changed transmission fluid with RL-MT90. Although, I might change it again and go to Amsoil since there was a lot of metal in the trans. I have a 2009rx8 p66m gearbox.
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Old 01-04-2016, 12:03 AM
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Originally Posted by ASH8 View Post
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Could not agree more Jason..

For the record...I must be living on a different planet, with both my P66M trans 'force when changing' is not needed, sure when cold 2nd can be a bit of a pain, I just drop it in @ slower speed/rpm, once warmed up a little it is fine.

I will bet my (you know), that Synchro's are brass, the Carbon 'coating' wears off, it has to be a softer metal (brass), every ring I used to sell in Mazda's gearboxes were/are brass.

I could be wrong with current Trans, but I doubt it.

There is a reason 'why' a GL4 oil has to be used in your Trans.

Here is what Redline says about their MT90.

75W90 GL-4 gear oil (similar to SAE 5W40/10W40 engine oil viscosity)
Popular in Nissan, Mazda, Mitsubishi, VW/Audi, Lotus Elise/Exige, Toyota
Offers quicker shifts, perfect synchronizer coefficient of friction
Safe for brass synchros, as it lacks the reactive sulfurs found in most GL-5 oils that cause damage
High performance gear protection and longer synchro life
Eliminates notchy shifting, even when cold
Satisifies the gear oil viscosity requirements of 75W, 80W and motor oil viscosities of SAE 40, 10W40, and 15W40
Recommended for GL-1, GL-3, and GL-4 applications, as well as where most special synchromesh fluids are specified


Red Line Synthetic Oil - Gear Oil for Manual Transmissions - MT-90 75W90 GL-4 Gear Oil
I agree. A less slippery GL4 will help. Fixxed mine.
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Old 01-12-2016, 03:48 AM
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Synchros in Mazda MTs are brass, with later cars using brass with a black "carbon" coating which wears off after use.
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Old 01-14-2016, 11:53 PM
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Gearlube

Filled my 2010 R3 with Motorcraft Synthetic Man Trans Fluid 75w 90. Its a GL3\GL4.
Works great. Low Sulfer GL4 rating wont damage the synchros.
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