ok everyone, I ordered some redline fluid (originally wanted MT90), but after some back-orders and some lost UPS packages... I ended up with Redline 75w90 Gear Oil in my hands. I probably agreed to this, but I can't remmeber now after all the confusion.

after such a long wait, I'm really eager to get this thing done, but is 75w90 Gear Oil ok to put in the transmission?

1990 NA GXL

 

is it 75W90 NS or just the regular 75W90.

The regular 75W90 is only a GL4 oil and probably not great, while the 75W90 NS is a GL5, as Mazda recommends in the tranny and rear end.

 

I'm reading the label...

SAE 75w90
GL-5+ Hypoid Gear Oil

no mention of NS, however.

 

If it is GL5 then it is fine although you won't see the upgrade in performance that Redline SuperLightweight Shock proof would give you at that same grade.

 

no no no no no no no gear oil in the tranny.

it'll eat all the brass and your tranny will be garbage in a week.

 

Mazda specifies 90W GL-5 Gear oil for the tranny

 

i use mobil-1 gear oil in mine? anything wrong with that??

 

w00t!

just got off the phone with Rotary Xecret 7 (the seller) and apparently the box I'm holding is the one that got lost last month! furthermore, the replacement they sent IS in fact MT90, and should be here end of this week.

I guess this means I have time to assemble the air pump setup described on Aaron Cake's website

just to double check; MT90 should perform better in my 5-speed than the 75w90 GL-5+ Gear Oil would have, correct?

 

Yes, MT90 is the recommended fluid for your transmission.
75W90 from Redline is not recommended for your transmission due to sulfate additives that attack the synchros.  Use only GL-5 stuff that explicitly states for use in synchromesh transmissions.  If you have any questions on Redline fluids, please call their tech line listed on their products - they can tell you what is recommended and what is not.


-Ted

 

I just changed my 5 speed manual lube to Penn. 75w90 GL-5 and it won't go into 2nd until warmed up how bout Royal Purple syn or something like that? My turbo Ford specs ATF in the T-5 tranny and seems to shift much better than my 7.
________________
88 GTU

 

anybody else using Mazdatrix's NEO GEAR in their tranny? Didn't fix the synchro crash like they said it might, it just crashes "smoother" now, LOL

 

Where could i buy the redline oil, online of corse.

sincerely gildardo orozco

 

do a www.froogle.com search. it's like google, but only looks up retail items. sort by price, etc. rad like dad.

 

Ditto. Anyone know?

 

NOT A GOOD IDEA.
Mobil one synth. has a lot of sulfate in its solution. And, we, have BRASS syncros. Sulfur eats brass.
I have also heard that many of GL-5 fluids (like mobil-1) contain sulfur, but Redline, according to their website, does not.
::: Icemark, I have read many brilliant posts by you, and you recommend using Redline Superlight shockproof, which is GL-5 rated. You described that it increases performance, compared to GL-4 MT90. Redline specifies using MT90 for better "syncro performance" with "perfect coefficient frition for syncros". But the shockproof states that it has "lower internal fluid friction of an ATF viscosity". ---therefore, wouldnt the shockproof be "less nice" to the syncros as MT90 is?
I just need something that is nice to the syncros right now. Which fluid do you recommend?

 

To quote the redline website, on their product description about their gear oils,
"The extreme pressure chemistry used in many gear oils can be corrosive to brass and bronze used in synchronizers and bushings. Most gear oils are corrosive at temperatures of 200°F. Red Line Gear Oils are non-corrosive up to 300°"
so, redline, in all of the gear oils, (even in GL-5 ratings) seems to not use sulfur.
Not to smack on ya Ted, please correct me if I am wrong.
Shin

 

So...... since some gear oils apparently eat our synchros, how about popping up a list of things to check to see what's safe and what's not? Sulfer content for instance.

 

so what the hell are we supposed to put in our transmissions? i put 75w90 mobil1 full synthetic gear oil in mine and its been working great... whats all this talk of "sulfer eating our syncros" stuff? will it REALLY eat our syncros or is this just some technobabble that you all feel you have to warn us about? does anyone have any proof of this?

 

maybe the sulfur combines chemically with something in the (old?) tranny oil & forms sulfuric acid, which, as we all know, will eat ANYTHING!

 

no, if you put sulfur on bronze or brass (which rx-7 syncros are made of) it will eat it. Mobil 1 has high sulfur content. (which is good for other kind of trans. which is not made of bronze or brass)
just chemistry.
Shin

 

bah

 

This stuff made my transmission shift better then amsoil synthetic. I was VERY pleased with it.

 

I heard good results with Neo, Amsoil, and Redline.
All I heard bad about is the Mobil 1.
Just make sure whatever you get, doesn't have too high of a concentration of sulfur in it.
Be nice to the syncros.
Shin

 

dam, maybe that's why my last tranny screwed up. i guess i'd better change it then. it does shift funny tho.

 

All the old mechanics I know say don't use anything that stinks in the transmission.

Redline tech has always recommended MT90 in the trans, and that what I use and recommend.

I know the 75W90 stuff stinks pretty badly, so I won't use it in the trans.

And yes, sulfates will eat the brass synchros.  I've seen "cheap" gear fluid used in an FC trans, and shifting started to snap, crackle, pop like th cereal.  Changing it back to Redline MT90 fixed this problem immediately.



-Ted