nycgps

iTrader: (1)

Right, damn, I forgot about that ! lol ! I kept on thinking its the other way around (calls for GL5 instead of 4)

jesus ... lol

Ok, NS will not work. I just changed the oil so I guess Im just gonna wait a bit b4 I pour it out and use Redline MT90. Thx

TeamRX8

iTrader: (25)

Oh great, another expert The Mazda RX-8 Manual Transmission (Y16M-D) Service Manual calls out 75W90 in either API Service Spec GL4 or GL5.

The issue is whether or not the oil has limited slip lube in it, which most standard gear oils do. The "NS" designation for Redline means it doesn't have limited slip lube added which isn't good for synchro engagement. This is why people using Royal Purple gear oil are having grinding synchro issues. If you insist on using Royal Purple you need to be using the Synchromax gear oil. If you want to use Redline my recommendation is MT-90 (a 75W90 GL4), 75W90NS (GL5), or 75W140NS (GL5). Racers can also use Shockproof Heavy.

Redline MTL isn't heavy enough. If you push it hard with this lube the trans will eventually have a catastrophic failure. I know, it cost me trans #2.

ken-x8

Even if there was unanamous agreement here that 5w20 was the best weight, you would not do any harm using 5w30. There's a long standing car guy tradition of using one weight higher than the official recommendation. Tom McCahill always stood behind that principle. (Also using single weight non-detergent oil, but times were different back then.)

You might look up the thread on the disassembly of Expo1's engine for oil insights by some pretty knowledgable folks.

Whether you go dino or synthetic, 5w20 or 5w30, make sure that the specifications for each kind of oil match what the owner's manual says. There's a TSB on the rear end oil, giving an alternate if what's specified in the owner's manual isn't available.

Ken

gundarx

Sorry I didn't intend to come out as an expert.. I was bouncing all over the place while hunting for the proper tranny fluid too but my 2007 owner's manual
(page 375) states "API Service GL-4 (SAE 75W-90)". Anyway, I accede to your better understanding of our tranny

nycgps

iTrader: (1)

so my brain in fact is functional ! Cuz last night I was like "Hmmm really ? I thought the tranny box works with GL4 and 5 and the Rear diff is 5 ????" Is not ? ... IS the other way around ? ...... ?????? " ...

phew .... My brain is working .... yes ! ....


Im gonna go get some 75w90NS then. See if it helps my Tranny whine issue. I have this issue B4 and after my clutch swap so its not the clutch pedal issue. (I will adjust it later the day, however)

Thanks Team

Jax_RX8

The original recomendation (2004-6) was for a GL4/GL5 combo fluid for the trans.

After countless trans failures due to syncro wear, the recomendation was changed in 2006 to a GL4-only manual tranmission fluid.

Not really - the limited slip additives do wear on syncros and oils with this should not be used, but the main issues are the specific Extreme Pressure (EP) additives (that are required to meet GL5 specs for gear oils) that are very hard on the soft metals used for many syncros. GL4 oils do have some antiwear additives, but not the ones that are so hard on syncros.

This does cause a tradeoff dilema, to get less wear on the syncros, you have to have less EP additives, which creates the potential for more wear on the trans gears themselves - but most of our trans failures are due to syncro failures (or slow working syncros causing poor shifts breaking gear teeth) and not due to actual tooth wear (with the possible exception of the pure racers like Team)

Possibly - depends on application. I know you race and you need a high viscosity oil with lots of EP additives for the very high temps and extreme loads you see.

But for the average mostly street driven vehicle, MT90 straight will provide very good protection and if you mix 50/50 with MTL, you would still have good protection with much better shifting. I would not do the latter for racing applcations, but for normal street use, it could be a good compromise of protection and good shifting.

Also, here is RL's actual recommendations for transimission via their brochure

"TRANSMISSIONS - MTL® can be used in most manual
transmissions and transaxles for both street and racing
use unless the manufacturer requires the additional protection
of an SAE 90 or the extreme-pressure protection
of a GL-5. In those situations the MT-90 (GL-4) or
75W90NS (GL-5) will provide good shiftability and synchro
compatibility and extra gear protection.
LightWeight Gear Oil can be used in transmissions calling
for a 75W or 80W GL-5. 75W140NS will provide
greater high-temperature viscosity, reducing gear noise
and rattle. D4 ATF can be used where the manufacturer
calls for an ATF as the D4 has GL-4 gear protection
and provides the best low-temperature shiftability."


While some tranmissions are designed to handle non limited-slip GL-5 gear oils, our trans has been having issues with it due to our syncro's soft metals, causing issues over time and thus the changing of the recomendation - your choice, but I do use a GL-4 only and would recommend avoiding any GL5 or combo GL4/GL5 gear oils in your manual trans.

nycgps

iTrader: (1)

Im researching the issue atm, and I ran outside b4 just to get myself a few bottles of MT-90 (Damn its fuxking expensive to buy them locally, 13.99 per quart + tax ! Argh !)

Now Im wondering, is my syncro still good or is it about to go. Like I said now whenever I shift @ faster than 30 mph I will get that *BOV kind of whine*.

meh ... How much is a rebuild tranny selling for again ?

Jax_RX8

Could be that you have some syncro wear - it is hard to tell because our syncros whine with the stock fluid (and some others) pretty bad, so it may or may not be from wear.

I think I mentioned before I have had success and almost totally eliminated any whine with the BG Syncroshift II (which is their full synthetic GL-4). It is slightly thinner than the 90 weight that is called for in the manual, so it is great for street use but likely not thick enough for tracking/racing, but has a great additive pack and shifts very, very well. It is a little hard to find, but almost everyone that has tried it swears by it.

RL's MT-90/MTL are also great GL-4 fluids for protection (not as good as the GL-5, but is it worth it), but MT90 is not known for being very good for shift quality unless you mix it 50/50 with MTL. MTL shifts great, but with a thinner gear oil that would likely be fine for normal street use, except for very hot climates.

RP's MaxGear 75W90 combo GL4/5 is a great fluid from a protection standpoint, I would just be concerned on the EP additives (and limited slip additives) causing increased syncro wear over time. For a trans designed to handle it, it is great, but I am not sure our syncros will hold up over the long haul using it. For the diff, it is great to use.

AMSOIL also makes their equivalent to RL's MT-90/MTL (MTG/MTF) that are GL-4 only, also very good, and could be combined 50/50 for a similar shift feel to an RL 50/50 mix.

As persnickiny as our trans is, I am not sure I would go with any lessor brands than these.

gundarx

Thanks Jax

Your input on oil matters, as always, is appreciated

Charles R. Hill

iTrader: (7)

He's my singular resource for automotive fluids and has never steered me wrong.

nycgps

iTrader: (1)

The whine is getting *worst* over these 2-3 K miles. So not sure if its really that bad or Syncro is about to *go*.

but I mean our tranny is known to be one of the weakspot, so Im not surprise if it dies.

Im gonna try to pour some MT-90 into the tranny either today or wednesday and see what happens. If the shift quality is bad (or grinds ..) then Im gonna mix it with MTL or try BG.

Even if my tranny dies, I can still go back and tell those dealership suckers to fix it, since I still have my receipts for Tranny fluid, and I change my fluid like almost every 15K miles.

Thx for ur words

Jax_RX8

Thanks for the kind words - happy to share what I can.

LionZoo

I always though the BG Synchroshift II was a 75W90...

Jax_RX8

No - it is a 70W80, a little thinner - about like mixing RL MT90 and MTL in a 50/50 mix.

Charles R. Hill

iTrader: (7)

I hate to engage in "toldja so" proclamations but I have been telling you guys for quite a while now that the factory-spec oil in the driveline is the best choice for street driving. There was a point a long while back where MM and I discussed in a thread the potential that the clinging/thicker oils weren't flowing as Aisin had intended and that they were causing the synchros to not slide or spin-up as freely. I have tried all different kinds of tranny fluids and the $8/qt. Mobil1 has always worked great for me.

Arrrrex-8

I ran a mix of this and Red Line heavy duty shock proof in my all wheel drive eagle talon. This combo worked great on that car. The 170,000 mile original transmission shifted beautifully and held up to repeated 500 hp drag launches with no issues.

I've had my RX-8 almost two weeks now, it shifts great. But I have no idea if the original owner ever changed the tranny or diff fluids so I've been planning on doing this in the near future. Would this be a good setup for my RX-8? Or is there a better option since mine doesn't exhibit any shifting problems?


Heres were I bought it for my talon. http://www.slowboyracing.com/estore/home.php?cat=5304


I've also got a '93 Miata I use for STS2 autoX. I put Royal Purple in it and it works great in the spring, summer, and fall months. But in the cold winter months the tranny grinds the first couple of shifts, so I think I'll stay away from it for my RX-8.

Lil_Gato

has anyone ever been denied a new transmission from mazda?
because i was told that "This is the last transmission were giving you"
im on my third one, first one went out when i first got the car, second one went out due to the syncros..?

and i found that the 5w20 oil burns up much much quicker than the 5w30.

nycgps

iTrader: (1)

Tons, depends on what ur dealership do.

Jax_RX8

Interesting mix, but I would still shy away from the RL Shock Proof in the trans as it is a GL-5 oil - try the straight BG Syncroshift II and see what you think or use a combo the BG and RL MT-90 as it is a GL-4 only oil if you want to tray something similar to what you used before.

Thanks for the link - this is a good place to buy BG trans/gear oils that I have seen many people use - good descriptions of oils as well on site.

The Miata uses a very similar (almost the same) trans as the 8 - you are experiencing what many others have highlighted using RP MaxGear in the RX8 trans - like I said above, I would shy away from this for the trans of an 8 or a Miata (great for the diff though)

savedsol

As far as engine oil I use Havoline 5W-30 or 20 in the winter. I'm about to start mixing in a qt/liter of Motul 300V 5W-40 every oil change and probably as the filler in between changes since it is safe to mix with non-sythetics. Crazy expensive but I think the best solution if you don't want to take the full-on synthetic plunge.

http://www.p1-performance.com/pdf/30...5W-40_3601.pdf

Already have 2L of the MotylGear 75W-90 for the trans just haven't put it in. The removal of GL5 specs has me hesitant as it's a GL4 & 5. Safe for all yellow metals though so I will put it in.

LionZoo

I'd have to agree with this here. My tranny felt best when it was still on the stock oil. The question is, where can we get our hands on the stock oil that came with the tranny?

Charles R. Hill

iTrader: (7)

I just use 75-90 Mobil1 as a factory-like replacement.

Jax_RX8

But remember Charles, M1 Gear oil is a GL-5 oil (I don't even think is is a combo GL-4/GL-5) and most others over the counter are the same - I would still stick with a GL-4 only fluid.

dothackRAVE

The dealer did my first tranny fluid change for me, and it felt far smoother than the factory one. They didn't tell me what it was, except it was "synthetic". This mystery oil is still in my tranny..., and I don't get any of the whining or problems some of you seem to be facing.

Anyway, thus far, I have decided the following for my engine:
-Castrol GTX 5W30 for the engine.
-Redline 75W30 for the diff

No idea what I should pick for the tranny still..., Jax? I just want one that is the best damned thing money can buy.

TeamRX8

iTrader: (25)

it you granny shift that 50/50 recommendation is fine, push it hard and you will pay the price ...