Transmission Fluid Change
06-16-2011, 06:30 PM
#26
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Np Texas, glad you got it sorted out and you didn't have to pay to have it done. It's better to be safe than sorry (and constantly worrying about it haha).
@ Ash8: The problem is most long term forum members are S1 owners who have a completely different transmission. If you read the Miata forums (links I posted above), their long term members mostly seem to aggree that the Motorcraft oil IS better than MT-90. Even so, the MT-90 is certainly good enough for most S2 owners. But if you're like me and really want the smoothest shifting transmission possible, the Motorcraft fluid is worth a try.
I will warn you though, the Motorcraft is twice the price of MT-90, so you really have to want the smoothest transmission to use it. Notchy transmissions are one of my pet peeve's.
@ Ash8: The problem is most long term forum members are S1 owners who have a completely different transmission. If you read the Miata forums (links I posted above), their long term members mostly seem to aggree that the Motorcraft oil IS better than MT-90. Even so, the MT-90 is certainly good enough for most S2 owners. But if you're like me and really want the smoothest shifting transmission possible, the Motorcraft fluid is worth a try.
I will warn you though, the Motorcraft is twice the price of MT-90, so you really have to want the smoothest transmission to use it. Notchy transmissions are one of my pet peeve's.
06-16-2011, 06:40 PM
#27
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^ I may likely give that Motorcraft fluid a shot next time I feel my car is due for a change. I don't mind paying extra if the product is better... Wait a sec, I better not start the debate, lol! 
06-17-2011, 11:03 AM
#28
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Thread Starter
Sweet, make sure you post a comparison if you do, I wanna know if the Motorcraft is actually worth it haha.
Ill probably do the MT-90 next year just to see.
Ill probably do the MT-90 next year just to see.
06-28-2011, 09:11 PM
#30
I changed my transmission(GL4) & rear diff.(GL5 ) with Amsoil at 2,700 miles because my diff. was having that chatter vibration when taking turns. The diff. was really black at 2,700 miles but the transmission was not that bad. I went with Amsoil because it did wonders for my 4Runner. Now, with the oil changes, the car shifts smoother and no more chatter from the diff. I will try the the Redline products for my next change.
05-23-2012, 09:34 PM
#31
Registered User
I have an '04 GT with 48k miles, which I purchased this past Jan. She's my first rotary, and I'm definitely a Honda convert. I love my 8. None of the previous owners have given it the love it really has needed so I've been going down the maintenance list: plugs, coils, wires, and the fluids. I changed the trans and rear diff. with redline fluids, MT-90 for the trans and 75w90 for the rear diff, after reading the praise from others here. Trans shifted amazing right afterwards. I could really feel a difference, which is no surprise since it probably had the original fluid with 43k miles on it. 
Now about 5k miles after the change, I've really started noticing that it doesn't shift as smoothly. I actually ground second gear the other day, which was a first. Also, I have noticed that on days when it is 90+ degrees out. It is super slick. Even on days with the temp in the mid 70s, I can tell it struggles to go into gears. Thinking motorcraft might be a better option. Anybody else having this problem after switching to redline? Thoughts? Ideas?
Now about 5k miles after the change, I've really started noticing that it doesn't shift as smoothly. I actually ground second gear the other day, which was a first. Also, I have noticed that on days when it is 90+ degrees out. It is super slick. Even on days with the temp in the mid 70s, I can tell it struggles to go into gears. Thinking motorcraft might be a better option. Anybody else having this problem after switching to redline? Thoughts? Ideas?
05-23-2012, 09:59 PM
#32
Redline is great right off the bat but it started getting worse for me as well. Especially on 3 to 2 downshift under hard braking, even with perfect revmatch it would always give me grief. Switched to Eneos and never looked back. Have had 0 problems ever since.
05-23-2012, 10:42 PM
#33
Super Moderator
Gee this becomes an almost boring topic, done to death...again.
Now, as I see it, with all things being equal, that is Transmission in 1st class condition and Synchronizer Rings (cones), Gears and Bearings included, then look at ambient temperatures and gearbox temps and use.
Again if the car and Tranny only does short driving distances then the owner has the problem not the car or oil.
I don't care what brand of Gear Oil one uses as long as it is GL4 rated, you will be fine.
Each have their own characteristics and operational range/design.
Yes, some brands have different feel and appears to be "a" 'better' product, but again it depends on use will depend just how satisfied one is.
Motorcraft or Ford is a thicker gear oil, so it can give better gear changes on colder boxes, but, when hot I believe thinner is better.
Redline is a thinner gear oil, when stone cold it is a little disappointing, but when gearbox is warm to fully hot operating temps, IMO it is one of the best gear changes and gear oils.
Eneos, Mobil, Shell and BP/Castrol I have not tried/tested, I have stuck with Redline as I like it's performance when my Transmissions are fully hot...both in my RX-8 and Miata/MX-5/Roadster.
Now, as I see it, with all things being equal, that is Transmission in 1st class condition and Synchronizer Rings (cones), Gears and Bearings included, then look at ambient temperatures and gearbox temps and use.
Again if the car and Tranny only does short driving distances then the owner has the problem not the car or oil.
I don't care what brand of Gear Oil one uses as long as it is GL4 rated, you will be fine.
Each have their own characteristics and operational range/design.
Yes, some brands have different feel and appears to be "a" 'better' product, but again it depends on use will depend just how satisfied one is.
Motorcraft or Ford is a thicker gear oil, so it can give better gear changes on colder boxes, but, when hot I believe thinner is better.
Redline is a thinner gear oil, when stone cold it is a little disappointing, but when gearbox is warm to fully hot operating temps, IMO it is one of the best gear changes and gear oils.
Eneos, Mobil, Shell and BP/Castrol I have not tried/tested, I have stuck with Redline as I like it's performance when my Transmissions are fully hot...both in my RX-8 and Miata/MX-5/Roadster.
07-17-2012, 06:43 AM
#34
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ALL the RX-8's Series 1 or 2 use the same Oil's, BUT...
The Oil for the Diff and Transmission is NOT the same, one is GL4 and the other is GL5.
Your "shop" is WRONG by using Idemitsu 75w90 for BOTH.
I use REDLINE...
MT-90 GL4 75W90 for Transmission.
75W90 GL5 High Performance Gear Oil for Differential.
They (shop) have used a GL5 in your Tranny...WRONG!...get it out ASAP.
The Oil for the Diff and Transmission is NOT the same, one is GL4 and the other is GL5.
Your "shop" is WRONG by using Idemitsu 75w90 for BOTH.
I use REDLINE...
MT-90 GL4 75W90 for Transmission.
75W90 GL5 High Performance Gear Oil for Differential.
They (shop) have used a GL5 in your Tranny...WRONG!...get it out ASAP.
07-17-2012, 06:44 AM
#35
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You are getting a bit confused by the specs - the Redline MT-90 that people use in the tranny IS a 75w90 oil. So it's not 90w.
And then GL-5 rated 75w90 in the diff.
I think the tranny is too stiff with 75w90, so I am the guy from that thread that uses a little Redline MTL, which is rated 75w80, but seems much thinner (makes no sense!)
I heard the 2006 manual actually says 75w80 if you can't find 75w90.....
But get the GL-5 rated oil for the rear end, tends to be very slippery, due to additives that contain sulphur. These same compounds can attack brass/copper etc. which are in the gearbox. So the specs call for "GL4" for the box. Basically the same stuff, but no sulphur.
And then GL-5 rated 75w90 in the diff.
I think the tranny is too stiff with 75w90, so I am the guy from that thread that uses a little Redline MTL, which is rated 75w80, but seems much thinner (makes no sense!)
I heard the 2006 manual actually says 75w80 if you can't find 75w90.....
But get the GL-5 rated oil for the rear end, tends to be very slippery, due to additives that contain sulphur. These same compounds can attack brass/copper etc. which are in the gearbox. So the specs call for "GL4" for the box. Basically the same stuff, but no sulphur.
07-17-2012, 06:46 AM
#36
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Well frankly, I totally agree with Stealth..
Why would Mazda JAPAN stipulate two separate 75W90 GEAR oils??
And again I don't give a crap what some "rotary" shop says, they like all the others are not Official Mazda Dealers nor do they receive ANY official notifications concerning the product, nor do they officially represent Mazda in anyway..everyone is an expert until something goes wrong.
From memory, I don't think older Mazda's with different transmission designs use GL4's...I could be wrong without checking..but that is not the issue.
If you have the time READ back in this thread to "others" who have gone against Mazda recommendations and to those who have had G/Box issues using the wrong rated or spec gear oils.
EDIT:, Sorry, Not this thread, but there is one around here somewhere....
Anyway Texas, if I was you I would have it changed out.
Why would Mazda JAPAN stipulate two separate 75W90 GEAR oils??
And again I don't give a crap what some "rotary" shop says, they like all the others are not Official Mazda Dealers nor do they receive ANY official notifications concerning the product, nor do they officially represent Mazda in anyway..everyone is an expert until something goes wrong.
From memory, I don't think older Mazda's with different transmission designs use GL4's...I could be wrong without checking..but that is not the issue.
If you have the time READ back in this thread to "others" who have gone against Mazda recommendations and to those who have had G/Box issues using the wrong rated or spec gear oils.
EDIT:, Sorry, Not this thread, but there is one around here somewhere....
Anyway Texas, if I was you I would have it changed out.
I love those people who think they are smarter than the engineers who designed the car.
Why would Mazda bother to stock and spec TWO different 75w90 oils? Makes no sense at all.
The GL-5 is definitely more 'heavy duty'.
It has sulphur additives for extreme duty.
These additives are excellent lubes and make oils slipperier than a greased eel.
And they will eat the brass/bronze synchronizers right out of your gearbox.
It will run very smoothly, and shift like butter - right up until you hear the crunch and you are back here explaining that 'it won't go into second at all'........
GL-5 rear end
GL-4 gearbox
Why would Mazda bother to stock and spec TWO different 75w90 oils? Makes no sense at all.
The GL-5 is definitely more 'heavy duty'.
It has sulphur additives for extreme duty.
These additives are excellent lubes and make oils slipperier than a greased eel.
And they will eat the brass/bronze synchronizers right out of your gearbox.
It will run very smoothly, and shift like butter - right up until you hear the crunch and you are back here explaining that 'it won't go into second at all'........
GL-5 rear end
GL-4 gearbox
Texas, I agree with Stealth and Ash, you should deffinitely get that GL5 out of your transmission. The posts on those Miata forums (same transmission as us) are all pretty adament about not using GL-5.
On a side note, you might want to try the Motorcraft Full Synthetic I was talking about earlier instead of the Redline MT-90. My transmission is SOO smooth right now with that stuff in it, its amazing! At first it wasn't much of a difference but it has gotten noticably smoother after a month or two (the Miata posts said this would happen). I highly recommend this transmission fluid now! It also seems to like warmer temperatures a lot.
Also check out my DIY if you want to save some cash and not deal with that ignorant repair shop again, it's seriously just as easy as an oil change, maybe even easier.
On a side note, you might want to try the Motorcraft Full Synthetic I was talking about earlier instead of the Redline MT-90. My transmission is SOO smooth right now with that stuff in it, its amazing! At first it wasn't much of a difference but it has gotten noticably smoother after a month or two (the Miata posts said this would happen). I highly recommend this transmission fluid now! It also seems to like warmer temperatures a lot.
Also check out my DIY if you want to save some cash and not deal with that ignorant repair shop again, it's seriously just as easy as an oil change, maybe even easier.
Gee this becomes an almost boring topic, done to death...again.
Now, as I see it, with all things being equal, that is Transmission in 1st class condition and Synchronizer Rings (cones), Gears and Bearings included, then look at ambient temperatures and gearbox temps and use.
Again if the car and Tranny only does short driving distances then the owner has the problem not the car or oil.
I don't care what brand of Gear Oil one uses as long as it is GL4 rated, you will be fine.
Each have their own characteristics and operational range/design.
Yes, some brands have different feel and appears to be "a" 'better' product, but again it depends on use will depend just how satisfied one is.
Motorcraft or Ford is a thicker gear oil, so it can give better gear changes on colder boxes, but, when hot I believe thinner is better.
Redline is a thinner gear oil, when stone cold it is a little disappointing, but when gearbox is warm to fully hot operating temps, IMO it is one of the best gear changes and gear oils.
Eneos, Mobil, Shell and BP/Castrol I have not tried/tested, I have stuck with Redline as I like it's performance when my Transmissions are fully hot...both in my RX-8 and Miata/MX-5/Roadster.
Now, as I see it, with all things being equal, that is Transmission in 1st class condition and Synchronizer Rings (cones), Gears and Bearings included, then look at ambient temperatures and gearbox temps and use.
Again if the car and Tranny only does short driving distances then the owner has the problem not the car or oil.
I don't care what brand of Gear Oil one uses as long as it is GL4 rated, you will be fine.
Each have their own characteristics and operational range/design.
Yes, some brands have different feel and appears to be "a" 'better' product, but again it depends on use will depend just how satisfied one is.
Motorcraft or Ford is a thicker gear oil, so it can give better gear changes on colder boxes, but, when hot I believe thinner is better.
Redline is a thinner gear oil, when stone cold it is a little disappointing, but when gearbox is warm to fully hot operating temps, IMO it is one of the best gear changes and gear oils.
Eneos, Mobil, Shell and BP/Castrol I have not tried/tested, I have stuck with Redline as I like it's performance when my Transmissions are fully hot...both in my RX-8 and Miata/MX-5/Roadster.
Noted... and added mine with ceratec... half bottle front and other half for diff...
10-07-2012, 09:55 PM
#38
2009 RX-8 Touring
I used Redline MT90 for a while. Currently I'm back on the stock oil because I had to have the pinion seals on my transmission and differential replaced. I'm not sure if the seal failure has anything to do with the MT90 -- or the Group 5 oil I tried before, which turned out to be too slippery, and possibly reactive with transmission components. In any event, if the shifter feels notchy, an oil change is in order regardless of what you use. Just stay away from Group 5 oils.
10-08-2012, 06:09 AM
#39
Yeah it's definitely time for a good fluid change, only 27K but an 04 so it's safe to assume it was never changed. I might as well do the diff as well. I'll wait on coolant since I'm pulling the motor in about a month to work on over winter. Did I read correctly in the diff needs group 5 75W90 correct?
10-08-2012, 09:59 AM
#40
Not to jack, does anyone have any bad experiences running Amsoil fluids here on the RX8? On my Evo and s2000, they worked great. I was hoping to use the same brand in the transmission and rear diff. I have a 2009 R3 with almost 25K on the odometer and I was planning to do it either before I put her away for the winter or in spring. Thanks!
Last edited by blacksheep515; 10-08-2012 at 10:35 AM.
10-08-2012, 01:57 PM
#41
Super Moderator
Not to jack, does anyone have any bad experiences running Amsoil fluids here on the RX8? On my Evo and s2000, they worked great. I was hoping to use the same brand in the transmission and rear diff. I have a 2009 R3 with almost 25K on the odometer and I was planning to do it either before I put her away for the winter or in spring. Thanks!
Remember MT-90 GL4 for Trans, GL5 for Diff.
Having a Diff Pinion-Axle Seal or Extension Housing Seal leak can happen to anyone, anytime, it's not new.
10-08-2012, 02:49 PM
#42
No NONE, and I also use it on my MX-5 NC2 which has the same (exact) Trans internals as late S2's...I wont use anything but Redline.
Remember MT-90 GL4 for Trans, GL5 for Diff.
Having a Diff Pinion-Axle Seal or Extension Housing Seal leak can happen to anyone, anytime, it's not new.
Remember MT-90 GL4 for Trans, GL5 for Diff.
Having a Diff Pinion-Axle Seal or Extension Housing Seal leak can happen to anyone, anytime, it's not new.
10-09-2012, 04:46 AM
#43
Super Moderator
BTW:
I know guys rave about the Motorcraft Trans Fluid in the Miata Forum, however, I only use Redline, in both my P66M Transmissions, my MX-5 Trans is the very latest updated (current) unit made by Mazda (P66M's are a Mazda made trans not AISIN).
Anyway, the smoothness on my 2011 Miata/MX-5 with MT90 is just amazing, it is silky smooth.
No notchyness, no baulking or blocking when cold...when hot it is just a click/click stick movement at any RPM...bliss!!!
The best 6 Speed Manual Trans Mazda has EVER made...
I will say this again, and again, for warm to hot weather climates (like South Australia, Texas), the MT-90 IS the best, as it is not too thick or too thin...it is just right.
Also I know I have said this many times, but the recommended distance on factory (original) Gear Fluids are way too long...from new, change in the first 1000-2000 KMS or Miles, and then halve the recommended Mazda change intervals.
I know guys rave about the Motorcraft Trans Fluid in the Miata Forum, however, I only use Redline, in both my P66M Transmissions, my MX-5 Trans is the very latest updated (current) unit made by Mazda (P66M's are a Mazda made trans not AISIN).
Anyway, the smoothness on my 2011 Miata/MX-5 with MT90 is just amazing, it is silky smooth.
No notchyness, no baulking or blocking when cold...when hot it is just a click/click stick movement at any RPM...bliss!!!
The best 6 Speed Manual Trans Mazda has EVER made...
I will say this again, and again, for warm to hot weather climates (like South Australia, Texas), the MT-90 IS the best, as it is not too thick or too thin...it is just right.
Also I know I have said this many times, but the recommended distance on factory (original) Gear Fluids are way too long...from new, change in the first 1000-2000 KMS or Miles, and then halve the recommended Mazda change intervals.
10-09-2012, 09:45 AM
#44
BTW:
I know guys rave about the Motorcraft Trans Fluid in the Miata Forum, however, I only use Redline, in both my P66M Transmissions, my MX-5 Trans is the very latest updated (current) unit made by Mazda (P66M's are a Mazda made trans not AISIN).
Anyway, the smoothness on my 2011 Miata/MX-5 with MT90 is just amazing, it is silky smooth.
No notchyness, no baulking or blocking when cold...when hot it is just a click/click stick movement at any RPM...bliss!!!
The best 6 Speed Manual Trans Mazda has EVER made...
I will say this again, and again, for warm to hot weather climates (like South Australia, Texas), the MT-90 IS the best, as it is not too thick or too thin...it is just right.
Also I know I have said this many times, but the recommended distance on factory (original) Gear Fluids are way too long...from new, change in the first 1000-2000 KMS or Miles, and then halve the recommended Mazda change intervals.
I know guys rave about the Motorcraft Trans Fluid in the Miata Forum, however, I only use Redline, in both my P66M Transmissions, my MX-5 Trans is the very latest updated (current) unit made by Mazda (P66M's are a Mazda made trans not AISIN).
Anyway, the smoothness on my 2011 Miata/MX-5 with MT90 is just amazing, it is silky smooth.
No notchyness, no baulking or blocking when cold...when hot it is just a click/click stick movement at any RPM...bliss!!!
The best 6 Speed Manual Trans Mazda has EVER made...
I will say this again, and again, for warm to hot weather climates (like South Australia, Texas), the MT-90 IS the best, as it is not too thick or too thin...it is just right.
Also I know I have said this many times, but the recommended distance on factory (original) Gear Fluids are way too long...from new, change in the first 1000-2000 KMS or Miles, and then halve the recommended Mazda change intervals.
10-09-2012, 07:58 PM
#45
TRANSMISSION OIL REPLACEMENT
1. Position the vehicle on level ground. 2. Remove oil filler plug and drain plug, and then drain the oil.
3. Clean drain plug. 4. Install drain plug and a new washer.
(w)
RX-8 Transmission (Manual & Auto) Page 24
5.
6.
o 2748 N·m {2.84.9 kgf·m, 2035 ft·lbf} Add the specified amount and type of oil through the plug port for oil filler plug to near the brim of the port.
Tightening torque
Specified oil grade
o API Service GL-4 or GL-5 Specified oil viscosity
o SAE 75W-90 Capacity (approx. quantity)
o 1.75 L {1.85 US qt, 1.54 lmp qt} Install oil filler plug and a new washer.
Tightening torque
o 2748 N·m {2.84.9 kgf·m, 2035 ft·lbf}
This came right from mazda workshop manual for rx8, it says GL-4 or GL-5, I will not put GL-5 in my transmission due to the sulfur but I wanted to point this out.
1. Position the vehicle on level ground. 2. Remove oil filler plug and drain plug, and then drain the oil.
3. Clean drain plug. 4. Install drain plug and a new washer.
(w)
RX-8 Transmission (Manual & Auto) Page 24
5.
6.
o 2748 N·m {2.84.9 kgf·m, 2035 ft·lbf} Add the specified amount and type of oil through the plug port for oil filler plug to near the brim of the port.
Tightening torque
Specified oil grade
o API Service GL-4 or GL-5 Specified oil viscosity
o SAE 75W-90 Capacity (approx. quantity)
o 1.75 L {1.85 US qt, 1.54 lmp qt} Install oil filler plug and a new washer.
Tightening torque
o 2748 N·m {2.84.9 kgf·m, 2035 ft·lbf}
This came right from mazda workshop manual for rx8, it says GL-4 or GL-5, I will not put GL-5 in my transmission due to the sulfur but I wanted to point this out.
10-09-2012, 09:04 PM
#46
Metatron
iTrader: (1)
ALWAYS take the filler plug out before the drain - you don't want to drain the box and find the filler is seized and you can't get any oil in.
I tried every GL-4 fluid I could find, but nothing was smoother than Redline MT-90.
I actually mix in about 20%-25% Redline MTL, which is a little 'thinner', and gives me just the best shifts.
I tried every GL-4 fluid I could find, but nothing was smoother than Redline MT-90.
I actually mix in about 20%-25% Redline MTL, which is a little 'thinner', and gives me just the best shifts.
10-12-2012, 07:06 PM
#47
Just changed my transmission and diff fluid with the Redline products and simply put.
God has parted the heavens and taken an holy leak in my tranny and diff, no other way to really put it. All my previous shift problems are gone feels like a new box, tight and smooth. Would highly recommend this to all 8 owners out there for under 100 bucks and an hour of your time its auto cruelty if you don't do it.
God has parted the heavens and taken an holy leak in my tranny and diff, no other way to really put it. All my previous shift problems are gone feels like a new box, tight and smooth. Would highly recommend this to all 8 owners out there for under 100 bucks and an hour of your time its auto cruelty if you don't do it.
10-25-2012, 02:24 PM
#48
2009 RX-8 Touring
Not to jack, does anyone have any bad experiences running Amsoil fluids here on the RX8? On my Evo and s2000, they worked great. I was hoping to use the same brand in the transmission and rear diff. I have a 2009 R3 with almost 25K on the odometer and I was planning to do it either before I put her away for the winter or in spring. Thanks!
Stick with a group 4 oil.
Last edited by fyrstormer; 10-25-2012 at 02:26 PM.
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