The clutch material that the synchros are made out of is the same that is used in Auto trannies, and is only compatible with certain types of fluid. I personally have stuck with Mazda fluid for this exact reason. The synchro/clutch type material is made to work with this fluid. If you run the wrong fluid in an Automatic it burns out the clutches right? Then why would it be any different for these synchros. If they were the old brass ones which arent as strong, you could run what ever fluid you wish in them.

This is what I was told in every manual trans class and update I have had since this type of syncro has been used in our Chrysler trannies. Just because this is mazda I dont see why there would be a difference and all the problems people are encountering with fluids just proves my point.

Just alittle food for thought.

 

Well isnt the OEM fluid that Mazda uses 80w-90? And it felt a decent amount thicker than Redline MT-90 warmed up, and technically the MT-90 is 75W-90 so I dont think the the grade of oil has anything to do with the feel (within reason, obviously a THICK *** OIL will have a different feel then thinner oil) The grade of oil just shows its cold and warm temps, and normally oils around the same weight should have the same feel so I dont understand why the Redline MT-90 felt like water... But the Idemitsu should feel alot better, well thats what im hoping for. The water like feel of the Redline made me feel nervous even though it was easier to shift. I felt like I was going to grind whenever Id downshift from low to high RPMS...

 

Yea, good point. The manual recommends 75w90, but you're correct in that aspect. I just don't want to take the time to sort through a crap load of other brands to find one that works and just bump up the thickness some instead.

 

I agree just point is, what the hell is the fluid they're running since I can't seem to find it after all this reading

I suppose I could just show up at the dealer and ask for some over the counter.

 

Only problem with that IMO is that there HAS to be better fluid than the OEM fluid Mazda uses... I mean Redline has gotten nothing but RAVING reviews and has to be better than the OEM fluid somehow even though You and I have had bad experences, everyone seems to love it.

 

Well everyone loves apparently the MT-90 but if you read a lot as I have been all day there are a few people where MT-90 doesn't do anything, and not just for this car but other ones as well. Most of them resort to the heavy shock gear oil. I'm just not sure if that's a wee overkill or not.

As anyone who reads on this forum knows, even if the issues are nearly the same, the solution isn't always the same. MT-90 was a step backwards for me contrast to 30k old OEM oil.

 

Another factor is he said redline grind. Is the OP one of the people that like to push a bit more past redline? I have seen some folks drive rx's and they like give that little tiny extra rev past beeping. If you have problems past the red zone it would not really be Mazda's fault. Mazda sticks are some of the best in the world. I have been driving them since the rotary truck and only had gear grind on one car. An 82 GSL Rx-7.

 

Mazda sticks may be the best in the world, but what transmisson can spin as fast as the one on our car??? Not many...

 

Hmm... my two cents. Well I did a tranny oil change on my first flush at 30k, swapped it to the Redline stuff and guess what I hated it. Always had to warm up or be atleast a warm temp. outside in order for it to work properly. Being that, I figured I will try it again and I flused it a year later again to Redline, I don't know why? It seemed like it got worst after that. Now, My third flush was Motul and wow what a difference. Here is the catch, the fluid only lasted no more than a year... Yea weird I know, it was burnt after one year of driving and no track days either. So, now I swapped into regular brand Valvoline and on top installed Stage 1 Exedy clutch. Shifts are beautiful only except 3rd to 4th after 6k, like someone else said I too have to wait for the rpm to drop before shifting to avoid the grind. Till then I won't drive hard core and will take it easy an do some research on aftermarket tranny's or different material parts for rebuild.

Cheers

 

I'm on my third tranny right now at 54k miles and when it's cold out the thing wants to grind with just casual shifting. I had a 1988 Toyo Supra Turbo that I bought with 150k on the broken odometer and it shifted better than my 8 when it was brand new. I even installed a Stage II ACT clutch and bumped the turbo up 5 psi and it still smoothly power shifted into third gear barking the back tires.

In my 8 every day I am worried a gear will start to grind for the third time and my warranty is up now.

The one in the S2000 seems to do good.

The S2000 has the same tranny?

I've heard people say we are better off with the 1993+ RX-7 tranny, better ratio for acceleration and stronger.

 

Got some Redline 75w140ns on the way. The rep over the phone suggested this over the Heavy Shockproof some ran since it has less friction modifiers to prevent slip. He doesn't think it will do anything but we'll see. After all, I didn't have the 3rd-4th issue until I switched to the MT-90.

 

^That's because it's the same transmission.....

 

bro did u say that trans costs 8k?!?!?!? how much is a rebuild?? my synchros grind so easily!!! it litereally GRINDS MY GEARS (pun intended)

 

You can get a new trans for around $2500

The RX-8 uses an Aisin Transmission. They are known for making some of the best trannies out there, problem is and I dont know for other years but the fluid that came in the 04 you couldnt even get in the states so Mazda puts thier 75w-90 in them.

Being a Chrsyler tech we have a VERY nice Synthetic 75w-90 (very thin feeling just not sure who makes it for Mopar) that we run in the T56 in the Viper and I have a bunch of it in my cabinet at work. Only thing is with all the Trans issues after fluid changes that I'm going to stick with the Mazda fluid.

The very little difference that you get from Redline or Royal Purple etc isnt worth it to me to potenially have trans issues because the fluid destroyed the clutch material in the snychros

 

The dealer warranty papers said $1400 and change on each of my two rebuilds.

 

That's the price that Mazda pays for a rebuild or remanufactured trans. Chrysler pays 10% over cost for all warranty parts. I know of alot of other car manufacturers are the same way, I'm sure Mazda is the same. They look at it like "we sell it to you so we get a discount". It's the same way the techs get paid around 40% less on warranty work compared to CP (customer pay) work. The customer cost is about $2400 for a new trans, but that depends on wether the dealer has matrix pricing or not and that means depending on how much money the dealers parts dept has made at that time of the month it could cost more.

The automotive industry is weird when it comes to warranty work and being a tech really sucks when warranty work pays less. Companys also keep track of how long it takes to do each job and if the average time starts taking alot less they cut the time they pay you even more. Pretty crappyhow they treat thier techs.

 

So, today I am adjusting my clutch pedal because since new clutch install I had the pedal maxed out. I know with time I would have to adjust it I guess its that time. I have the Valvoline trans oil in there now, but here is what I noticed: When the car is just started and not warmed up it shifts better after 6k from 3rd to 4th??? Strange yes, when temperatures rise along with the weather it starts to act up... My two cents. Maybe I will just flush it back with Mazda fluid and see how that is, if any difference. I am coming to a conclusion that Mazda oil that was in there originally was better and ever since trying new fluids it has gotten RETARDDD.

 

I came to this thread to see any similarities with what I have been experiencing and sure enough when shifting near red line 3-4 gear is grindgin bad and this is my passing gear. I have recently switched to royal purple full synthetic engine oil and sure enough, the trans has been acting up ever since. Any chance this could be the cause? I have 48000Miles on my 8. Owned it new since Oct 2003.

 

I mean no offense, and you clearly know what you're talking about by reading your other posts, but the syncros in my '04 transmission ARE brass. I'm replacing my 4th gear syncro, which measured out to be a little worn. I would post up pics, but I haven't taken any.

Like I said, my tranny is in EXCELLENT condition after opening it up. The only problem was the broken bearing cover, that was inhibiting it from going into gear. After looking over the service records on file, I can only assume that after about 64,000 miles, the tranny was running on the original fluid, unless the previous owner changed it himself (not likely considering the car was purely stock when I purchased it).

In light of my discovery, I'm absolutely sticking with STOCK fluid for the tranny. It seemed to hold up very well, as is evident by the condition of all internal components. The shifting was crazy smooth and I loved it. It's actually quite disappointing to hear the problems other people are having with tranny fuild. Thanks for your thoughts, as it helped solidify my decision.

Hahaha...this turned into a Tranny fluid thread!

 

I personly am a FAN of our tranny.

I have about 78k on th car and haven't had any issues what so ever. And some may call me an aggressive driver. So that's that.

 

So..what do you guys do, that is hard on these?

I run the heck outta mine on my daily mountain curvy drive 100mi a day in total.

I HPDE and instruct with NASA..hard.


Likely the only thing I do different that others are not..is I KNOW it takes time to make those redline RPM shifts..things break when you force them.

My SU car has been running in excess of 500rwhp in the stock 1995 6spd tranny that Pontiac shipped it with, and winning, also by driving the hardware as it wants to be driven...it's been in excess of that HP level since late 2000.


I could be wrong(tm), but the 'speed shifting' is what's bustin these up...its not a design issue.

 

I dunno..C'mon..how much torque is the tranny receiving during a shift?

I know...NONE!

Has nothing to do with power, just how it's being used...sure, its not a race car..sorry bout that guys.

 

It is well known the Royal Purple oil doesn't work well in the RX-8 transmission...

Do a little looking around...

 

Just last night I was double clutching ( Clutch in > Neutral > Clutch out > Rev > Clutch In > Gear > Clutch out) from 4th to 2nd and it didnt quite feel good, I know double clutching is better but it felt like it grabbed a little and notched 2nd a tad in a bad way. I wanted to throw-up... No more double clutching for me after that, Ill just leave the clutch in while I rev-match... Im worried 2nd is going to start grinding and acting notchy like my 5th gear did before I got it replaced.

Before I got my new 5th gear it would be very grabby, not in a good way, grind a little, then go in. It was like a "mini-grind" but it'd go in.

Worst part about all of this is my Warranty expries this month (June) on the 19th... So I gotta get my baby in and tell them what happened so its documented, so if later it does start to **** itself Ill have some proof I tried to get it fixed and they didnt...

Other than the 5th gear that crapped out REALLY fast and this incident last night with 2nd (only double-clutched twice, 2nd time was to see if I messed up the 1st time) my transmisson is good. It has weird quirks ( like my 3rd gear like falling into place but it feels like its rubbing something tough and sometimes engages hard) but no grinding issues...

 

+1
though i'm just a nub!

For simplicities sake though, it seems that the culmination of all my reading on the transmission and differential oil topic is that the Redline products are defintely safe to use.

I still need to really jump into the engine oil topic some more. but...