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Discussion Starter #1
My car has 178K on it, I've replaced the trans fluid with a good synthetic (75W90 Amsoil) and all other shifting is normal.

I'm getting a high pitch noise when I'm in 5th, it's not critical or too loud, but it can be annoying, and I'm thinking it's a bearing of sorts... question: can I replace the 5 spd with a 6 spd same year (I know they come in the Speed3)?



Thanks for any input...
 

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It is possible, but you will need to also replace the Shift Assembly, Flywheel, Clutch, Axles, Hubs, Shifting Linkage, I been thinking of doing the same thing, I am currently at 48k with my Mazda 3 07 GT Hatchback.
 

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Demon Spawn
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whine in gear cannot be a bearing unless the throwout bearing in your clutch is sticking, which would be noisy in every gear and cause clutch grab and slippage as well as rough engagement. whine in gear is usually a bad syncro. if its only one gear, did you use gl4 only fluid or gl4/gl5 rated fluid if you used the latter that maybe your problem mazda gearboxes (5speed) in the older 3s and proteges cannot use gl5 rated fluid as the gl5 additives screw up the syncros. gl4 only fluid is very tough to find these days but a mazda dealer should have some sitting around knowing this and waiting for your hard earned buck. you also should not have to change gear oil often. you can also get the gl4 only fluids online and i would advise doing so before dropping the time and money on a new tranny you may not need.
 

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Discussion Starter #4
Bingo... you may have the answer, it hasen't affected the other syncros, but it definitely was Gl4/5, I replaced the original with! I'll change right away... thank you so much!! Oscar Echo... (operator error) for sure!!
 

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Demon Spawn
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Bingo... you may have the answer, it hasen't affected the other syncros, but it definitely was Gl4/5, I replaced the original with! I'll change right away... thank you so much!! Oscar Echo... (operator error) for sure!!
the manual for my 08 does actually state gl4 or 5 can be used in manuals not in turbo cars. but turbo models should only use gl4. what brand of fluid did you use and did it have the limited slip additive in it? maybe try a mazda label fluid, it will have all the additives you need for the transmission and none you dont. that maybe your issue an additive that is messing with the syncro on 5. my protege did not like SYNTRAX™ LIMITED SLIP 75W-90 castrol fluid, must have had an additive that didnt agree with it. i had to take it out and use valvoline synpower gear oil with no issues, however valvoline recommends this for synchronized manuals like we have: Valvoline SYNCHROMESH - Manual Transmission Fluid | O'Reilly Auto Parts
personally if i were you since you are having issues get that stuff you have in their out and put mazda fluid in as a cheap way to see if it fixes or helps your issue
this is from my manual:

Lubricant Quality
Lubricant Classification
Engine Refer to the recommended SAE viscosity numbers on page 8-18.
Manual transaxle oil
Without turbocharger
Any temperature
API Service GL-4 or GL-5
SAE 75W-90
Above 10°C
API Service GL-4 or GL-5
SAE 80W-90

With turbocharger
API Service GL-4
SAE 75W-90

though the internals of the 6 and 5 speed are not too different so gl4 would be a better bet.
 

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Discussion Starter #6
I put in Amsoil Manual Transmission & Transaxle Gear Lube 75W-90... it is a GL-4 product but I had to supplement it with a GL-5 product because I didn't have enough... so... I'm going to take your suggestion and just use the Mazda gear oil... I don't recall any of this prior to the changing of the fluid, but that could also be age related! Thanks for the encouragement and info!
 

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Demon Spawn
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The mixing of fluids could do it, as well as age. My p5 actually did shift better with old fluid than new the first few months then it came back and shifted better than ever. Transmissions are nit picky.
 
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