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My 2005 6S has 60K miles on it and I decided to change the transmission fluid from the Redline MT90 that had been in the car since I did that swap back when the car was new (I am the original owner). I ordered 3 quarts of Neo 75W90HD fluid from http://www.bakerprecision.com and when the shipment arrived the weather was relatively warm (especially for Massachusetts) so I did the fluid change.

With the Redline fluid I thought the gearbox was pretty slick except for the occasional crunchy 2-3 upshift. With the Neo fluid in the box every shift is super slick. 1 finger shifting is the norm for me (I don't have any short-shifter installed - it's the factory shift mechanism) and we have temps down around 20F this morning and the car slid in and out of gear nice and easily. One additional plus with the Neo is that driving at highway speeds in 5th gear my transmission is silent - no faint whine that I used to have with the Redline fluid.

If I had to choose between Redine and Neo I would probably go with Neo again. The only reason that I wouldn't say 100% Neo is that I've had very good results with the Redline fluid for the past 3.5 years and only a week with the Neo. If the transmission continues to perform they way it is now though, it will be Neo from me for now on.

The fluid change itself was a piece of cake. Jack up the car and support with stands at both the front and the rear so that it's "level" even though you can get under it. Open the fill plug with a 10mm hex key (I have the 3/8" drive set from Craftsman and 10mm is the largest). Then open the drain and let it drain. Put the drain plug back in (wipe any filings off the magnet end of the plug even though mine was clean) and start pumping in the fluid into the fill hold until it starts to seep out.
 

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That stuff is damn good. I used it and the shop that put in the new clutch and Fidanza flywheel put Royal Purple in it. Huge difference. Ran the Royal purple for a few months and then put some Schaffers in it, that stuff is equally as good.
 

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QUOTE (itchyrichy @ Aug 2 2009, 02:00 AM) index.php?act=findpost&pid=1587948
Yep, no complaints at all. Throughout the cold weather of the winter and now the hot weather of the summer it's been perfect.[/b]
royal purple is crap it has sulfer in it you can smell it i dont care if it says gl4 safe ..sulfur eats yellow metals...does anyone know if their are yellowmetals in these trannys.. i only come to this board cause my cousin has a mazda 6 ive heard there where yellow metals can anyone confirm this? :slap:
 

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If I'm reading it right, isn't "75W90 HD Competition Gear Oil" a GL-5 oil? I thought GL-5 in our transmissions was bad...
 

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QUOTE (joebrez @ Nov 24 2009, 08:52 AM) index.php?act=findpost&pid=1618955
Drogos, I called Neo Synthetics. They said it's a GL2 thru GL6 fluid. The RX and Miata guys had nothing but great things to say about it. I changed mine over the weekend, it's like butter!!! A bunch of "gear whine" is gone also!!![/b]
...so Gl2 thru GL6 would make it GL5 also, no ??? :) which would be bad for our tranny ?? Might be smooth as hell but I don't care for it if my tranny goes bad in 20k miles or so. I don't have problems with my tranny at all and I testdrove Manual m6s that were an absolute pile of chunking crap in comparison to mine...so I don't want to screw up something that is not bad to start with. I do get some chunkiness (is that even a word :) ?? forgive me I am not a native speaker) in 1st and 3rd when cold but from what i read here it's the nature of our trannies. \
Can someone jump in please and clarify the GL-5 thing ...thanks much

EDIT: ok I got it the other way around I guess. GL2-GL6 would mean it is safe for trannies with those requirements. ..well DUH!!! :)
 

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QUOTE (justinhb @ Nov 9 2009, 05:44 AM) index.php?act=findpost&pid=1615214
royal purple is crap it has sulfer in it you can smell it i dont care if it says gl4 safe ..sulfur eats yellow metals...does anyone know if their are yellowmetals in these trannys.. i only come to this board cause my cousin has a mazda 6 ive heard there where yellow metals can anyone confirm this? :slap:[/b]
Correct,the RP will eat the yellow metals up,you have to get a GL5 that is yellow metal safe and non sulfur based. I run Schaeffer's in my trans.


QUOTE (joebrez @ Nov 9 2009, 08:42 AM) index.php?act=findpost&pid=1615235
If I'm reading it right, isn't "75W90 HD Competition Gear Oil" a GL-5 oil? I thought GL-5 in our transmissions was bad...[/b]
Not all GL5 is bad.....just sulfur based ones.


QUOTE (Drogos @ Nov 24 2009, 09:43 AM) index.php?act=findpost&pid=1618953
so...is it bad anyone ?[/b]
Answer is in above quote


QUOTE (joebrez @ Nov 24 2009, 09:52 AM) index.php?act=findpost&pid=1618955
Drogos, I called Neo Synthetics. They said it's a GL2 thru GL6 fluid. The RX and Miata guys had nothing but great things to say about it. I changed mine over the weekend, it's like butter!!! A bunch of "gear whine" is gone also!!![/b]
Neo is good but it is 3x price of other fluid on the market......


QUOTE (Drogos @ Dec 17 2009, 08:22 AM) index.php?act=findpost&pid=1623770
...so Gl2 thru GL6 would make it GL5 also, no ??? :) which would be bad for our tranny ?? Might be smooth as hell but I don't care for it if my tranny goes bad in 20k miles or so. I don't have problems with my tranny at all and I testdrove Manual m6s that were an absolute pile of chunking crap in comparison to mine...so I don't want to screw up something that is not bad to start with. I do get some chunkiness (is that even a word :) ?? forgive me I am not a native speaker) in 1st and 3rd when cold but from what i read here it's the nature of our trannies. \
Can someone jump in please and clarify the GL-5 thing ...thanks much[/b]
It meets the classifications of GL2-GL6.....

GL5 is bad if it is sulfur based fluid.
 

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QUOTE (Drogos @ Dec 17 2009, 08:22 AM) index.php?act=findpost&pid=1623770
...so Gl2 thru GL6 would make it GL5 also, no ??? :) which would be bad for our tranny ?? Might be smooth as hell but I don't care for it if my tranny goes bad in 20k miles or so. I don't have problems with my tranny at all and I testdrove Manual m6s that were an absolute pile of chunking crap in comparison to mine...so I don't want to screw up something that is not bad to start with. I do get some chunkiness (is that even a word :) ?? forgive me I am not a native speaker) in 1st and 3rd when cold but from what i read here it's the nature of our trannies. \
Can someone jump in please and clarify the GL-5 thing ...thanks much[/b]
Our manual (the book) in my car specifically says GL-4 OR GL-5. I also called Neo Synthetics and they said no issue using it in a GL-4 Transmission. Hell, when I asked the dealer what fluid they use, they said "Gear Lube, same thing we put in the differentials on the RX-8". My understanding is that alot of GL-5 contains Sulfur, which can eat the synchros. However, a GL-5 without Sulfur should be safe. In addition, the RX-7, RX-8, and Miata guys have been using this stuff for a while with nothing but great things to say about it.


QUOTE (joebrez @ Dec 17 2009, 08:56 AM) index.php?act=findpost&pid=1623781
Our manual (the book) in my car specifically says GL-4 OR GL-5. I also called Neo Synthetics and they said no issue using it in a GL-4 Transmission. Hell, when I asked the dealer what fluid they use, they said "Gear Lube, same thing we put in the differentials on the RX-8". My understanding is that alot of GL-5 contains Sulfur, which can eat the synchros. However, a GL-5 without Sulfur should be safe. In addition, the RX-7, RX-8, and Miata guys have been using this stuff for a while with nothing but great things to say about it.[/b]
From their Website:
"75-90 HD
Key Features:
-Designed for Street & Performance Vechicles
-High Quality, Race Proven Performance
-Rear End and Manual Transmission Application "
 

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QUOTE (joebrez @ Dec 17 2009, 08:58 AM) index.php?act=findpost&pid=1623781
Our manual (the book) in my car specifically says GL-4 OR GL-5. I also called Neo Synthetics and they said no issue using it in a GL-4 Transmission. Hell, when I asked the dealer what fluid they use, they said "Gear Lube, same thing we put in the differentials on the RX-8". My understanding is that alot of GL-5 contains Sulfur, which can eat the synchros. However, a GL-5 without Sulfur should be safe. In addition, the RX-7, RX-8, and Miata guys have been using this stuff for a while with nothing but great things to say about it.




From their Website:
"75-90 HD
Key Features:
-Designed for Street & Performance Vechicles
-High Quality, Race Proven Performance
-Rear End and Manual Transmission Application "[/b]
The thing they are not telling you is that it has a additive pack that breaks down over time and will produce acid and eat up the yellow metal...........NEO still has sulfur in it....just not as much as some others
 

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QUOTE (djquik1 @ Dec 17 2009, 08:02 AM) index.php?act=findpost&pid=1623783
The thing they are not telling you is that it has a additive pack that breaks down over time and will produce acid and eat up the yellow metal...........NEO still has sulfur in it....just not as much as some others[/b]
so R'U saying Neo should be good as long as it's not sitting there for too long? Where did you get that "acid forming over time" info from ?
 

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QUOTE (Drogos @ Dec 17 2009, 10:16 AM) index.php?act=findpost&pid=1623789
so R'U saying Neo should be good as long as it's not sitting there for too long? Where did you get that "acid forming over time" info from ?[/b]

It is a sulfur based fluid with a additive pack......like almost all of the GL5/GL6 fluids,over time and use the additive pack will break down similar how oil breaks down in your car.....thermal cycling,etc.
When the additives break down,acid will start sulfuric acid will start forming and it will eat the yellow metals up in the transmission..
 

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QUOTE (joebrez @ Nov 24 2009, 10:52 AM) index.php?act=findpost&pid=1618955
.. The RX and Miata guys had nothing but great things to say about it...[/b]
been runnin nothin but neo since the mid 90s on all the fds..
used redline and others before to find shavings during each change.. none on neo.. im usin em on my diffs as well..
 

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Well I was looking thru this thread as I am thinking it's time to finally change my mtx fluid and came across this after some googling...Red Line Synthetic Oil - Gear Oil for Manual Transmissions - MT-90 75W90 GL-4 Gear Oil

Then I go thru this thread and WHAT? lol Now I am really confused. I understand the gl stuff but it seems from what you guys are saying no matter which one we buy, over time, as with many fluids they break down and the properies have an effect anyway. Did a clear choice ever get picked? Mine is an 05 6i mtx.


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