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Old 09-04-2003, 10:22 PM   #1
avatarr
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Post Gear oils info revealed (long)

So I am originally starting this thread as a centralized location for all the questions that I have had about gear oils. I originally switched out my transmission gear oil for mobil 1 synthetic 75w90 at the recommendation of a friend. I enjoyed the new smooth feel of it but absolutely HATED the 2nd to 1st grind that came with it. I figured I might be able to live with it - after a few months I decided I couldn't take it anymore. Someone else recommended Red Line over the mobil 1 synthetic - specifically shock proof super light weight. I went to a local Red Line distributor and all they had was MTL, MT90, 75W90, 75W90NS and some others that I don't remember. My service manual called for 75w90 and I just wanted something that would work so I got the regular old 75w90 Red Line. I changed it out and the 2nd to first grind got worse. Why? Well, I decided to do some research.

Why does it grind after putting the new oil in?
great info on this *here*.
It's interesting to note that the type that Cobb Tuning has the "highest recommendation" for is Red Line MT-90, which just so happens to be GL-4 rated. More on this below.

According to raceshopper.com:
Red Line MTL is classified as a 70W80 gear lubricant satisfying the API Service requirements of GL-3 and GL-4. MTL also satisfies motor oil viscosities SAE 5W/10W/30, and the viscosity requirements for ATFs. MT-90 is a 75W90 GL-4 and also satisfies motor oil viscosities SAE 10W/15W/40. The additive chemistry used is non-corrosive, so even though they will provide GL-4 performance, they will not corrode synchros or bushings. Because of its low corrosivity, Red Line MTL and MT-90 could also be used in transmissions requiring GL-1 or GL-3 lubricants. Seal compatibility is designed to be similar to petroleum-based lubricants.

What is GL and MT-1 rating?
The gear oil's GL rating as set forth by API measures how well it will perform under extreme pressure. Gear oil is manufactured with anti-wear additives to stop metal surfaces from welding together. The GL rating ranges from 1 to 6. Gear oils rated 1 to 4 are considered anti-wear products, whereas GL 5 and 6 products are for use under extreme pressure.
GL-4
Denotes lubricants intended for axles with spiral bevel gears operating under moderate to severe conditions of speed and load or axles with hypoid gears operating under moderate speeds and loads. These oils may be used in selected manual transmissions and transaxle applications where API MT-1 lubricants are unsuitable.
GL-5
Denotes lubricants intended for gears, particularly hypoid gears, in axles operating under various combinations of high-speed shock loads and low-speed, high-torque conditions. Lubricants qualified under MIL-L-2105D satisfy the requirements of the API GL-5 specification, although the API designation does not require military approval.
MT-1
Denotes lubricants intended for nonsynchronized manual transmissions used in buses and heavy-duty trucks. Lubricants meeting the requirements of API MT-1 provide protection against the combination of thermal degradation, component wear and oil seal deterioration. API MT-1 does not address the performance requirements of synchronized transmissions and transaxles in passenger car and heavy-duty applications.

GL-5 has the following oil performance tests with stringent requirements:
ASTM L-33:
Gear test using differential assembly measuring the resistance to corrosion in the presence of moisture.
ASTM D-6121:
Gear test using complete axle assembly measuring the resistance to gear distress under low-speed, high-torque conditions.
ASTM L-42:
Gear test using complete axle assembly measuring the resistance to gear distress (scoring) under high-speed, shock-load conditions.
ASTM L-60:
Bench test using spur gears measuring oxidation stability.
ASTM D-892:
Bench test measuring foaming tendencies.

I also found this information from Red Line:
Most manufacturers of manual transmissions and transaxles recommend an 80W or 90W GL-4 lubricant. GL-5 gears oils which are required in hypoid differentials are not used in most synchromesh transmissions because the chemicals used to provide the extreme pressure protection can be corrosive to synchronizers, which are commonly made of brass or bronze. Typically, the use of a GL-5 lubricant in a synchromesh transmission will shorten the synchronizer life by one half. The extreme pressure requirements of spur gears and helical gears found in transmissions are not nearly as great as found in rear-wheel drive differentials. A GL-4 lubricant provides adequate protection for most manual transmissions, unless a unique design consideration requires the extra protection of a GL-5.
This leads me to believe that Subaru decided that this "unique design" was given consideration and requires the extra protection of a GL-5. So why does Cobb Tuning recommend a GL-4? That answer I do not have. What I did surmise from the above quotes is that the higher the pressure protection (GL rating) the more corrosive it is to brass or bronze synchros. You'll probably have to re-read the above quotes (in italics). It's okay... I'll wait...

What is API?
API is American Petroleum Institue. They set forth what they call service ratings (GL, MT, etc...) described above.

What are 02+ wrx synchros made of?
Bronze according to various threads on nasioc. No cold hard evidence yet but most say they are bronze.

What is SAE rating? (ie 10w30, 75w90, etc...)
I would say the good majority of people know what this means but in case you do not, go *here*.

So which gear oil should I use?
I know you were probably hoping for the tell all answer from all of this but my hope is that this is educational enough for you to make an educated decision based on the information provided. If it means anything, I am probably going to go with Red Line 75W90NS unless I find something that looks like a better compromise (gears/synchros) with GL-5 rating.

I hope this helps everyone out at least some.

-Jason

**Updates**
More information on oil properties / constituents:
http://forums.nasioc.com/forums/show...hreadid=415479

Gear oil used by Subaru dealerships (OEM)
Valvoline (non-synthetic) GL-5 75W90

What I ended up doing
I put 75W90NS (Red Line) in and shifting got a lot better. It doesn't grind anymore into first but I cannot shift into first at very high speeds still. It simply made the lockout from first work a little better and prevent me from grinding into first. I still rev-match to get in at higher speeds.
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Last edited by avatarr; 10-08-2003 at 06:04 PM.
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Old 09-05-2003, 02:43 AM   #2
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Good info... I found even more good info in this post.

Considering all that I've read in there, I am about to put Royal Purple Max-Gear 75W90 into my car and will be able to test it out within the next day.

Also, if you're using standard, off-the-shelf fluids in your car, you may want to take a look in the thread to see if your fluid is noted as having corrosive properties to the soft materials of your synchros.

Edit (re: Royal Purple): Since I decided to just stay up later and do it... I have to admit, this stuff is VERY nice. The only thing that was said about it was that the gears were louder, though I can barely tell. Mine whine a lot as it is, and my car makes a lot of strange noises, but I can't hear anything over normal when driving, just my standard 1st gear decel noise. Shifting has to take 40-50% less force to get the shifter to select the gear. Overall I'm very impressed.

Last edited by 8Complex; 09-05-2003 at 04:40 AM.
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Old 09-05-2003, 10:42 AM   #3
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I'm currently running RedLine 75W90NS. I think initially, you'll be very impressed with the results.

However, it seems, after a couple thousand miles....the shininess wears off and I start grinding when trying to get into first, again. I also grind going into fourth when I hurry it. I have to temper my enthusiasm going into fourth. But, I'm guessing this is one of those case-by-case basis things. Soooo, YMMV

My roommate is shocked that I would allow these condition to go on like this. So, I've been researching alternatives.

I think I'm going to spring for some of the Neo gear oli stuff, but it's PRICEY! Maybe the aforementioned Royal Purple might be the call. Maybe I'll try both and report back.

HTH
mike
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Old 09-05-2003, 10:43 AM   #4
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maybe we should run a poll to see what kinds of lubes folks have been happiest with?

ken
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Old 09-05-2003, 10:53 AM   #5
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it might not be a bad idea but it seems that it would have to be with the 02/03 wrx's as they are the ones that seem to have the most complaints when using various synthetics.

-Jason
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Old 09-05-2003, 11:54 AM   #6
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What do they use from the factory?
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Old 09-05-2003, 12:07 PM   #7
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Quote:
Originally posted by Yungimoto
What do they use from the factory?
I have read in other threads that they use valvoline though I haven't been able to confirm it first hand from anywhere. If I find anything out for sure, I will edit it in the **updates** section at the top of the thread.

-Jason
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Old 09-05-2003, 12:40 PM   #8
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I am not certain what they run from the factory. FHI does have a "hybrid" oil that some of the dealerships in my neck of the woods use. It supposedly will help the tranny shift better. It did not solve the grinding/balking issues on my first tranny. Have not tried it on the second.
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Old 09-05-2003, 01:40 PM   #9
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I second RP MaxGear. GL-5 rated and non corrosive for yellow metals. Nice smooth gear engagements, very impressive low temperature performance (Redline 75W90NS sucked at that).
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Old 09-05-2003, 02:30 PM   #10
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Default Royal Purple Max Gear

I recently installed the Royal purple max gear into my tranny fluid and rear differential. The first day testing went awesome. Everything shifted really smoothly. Into first and reverse without the usual clicking noises. I noticed however when downshifting into first that the syncros make alot more noise and shifts are as smooth when matching speeds. I think my syncros aren't working as well as they did with the stock fluid.

After about a week the shifting seems to be the way it was with the stock fluid, not better not worse.

I guess it's just a "peace of mind" to know i cleaned out all the ugly metal that was on the magnet transmission bolt and rear differential magnetic bolt.

Today (9/5/03) i will install the Kartboy SS and bushings and bushings when i get out of work. I post reviews.
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Old 09-05-2003, 02:52 PM   #11
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I've tried stock, Redline MT90, and Neo Synthetic 75w90RHD . I feel that both the redline and neo are better than stock, allowing for smoother, quicker shifts. The neo synthetic feels better than the redline; every shift is smoother and faster, and it also allows me to shift from 2nd to 1st at higher rpm's (when using proper double-clutching and rev-matching).


One thing I've noticed is that almost any gear oil will feel like crap when it's old, change it every 15K, as per the owners' manual. Most enthusiasts should follow the shortest recommended maintenance intervals.

-scott-
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Old 09-05-2003, 03:00 PM   #12
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Default RP

It was great for about 500 miles, and then the grinding started. I am at 56k miles, 02 5spd wrx sedan. I am going to go back to dino (Castrol 75w90) and continue RP in the Rear Diff. I have been running it for about 20,000 miles. I hope the plug shows no signs of problems (magnetic drain plug)'.
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Old 09-05-2003, 03:19 PM   #13
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I have tried 7590NS, royal purple, and Torco, in my car, and none can help my 2>1 shift.

I'm about to try Neo or some sort of lightweight oil perhaps soon. Ah heck who am I kidding, I want a new tranny!
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Old 09-05-2003, 04:32 PM   #14
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I have used the Redline 75-90NS for the last 35+ thousand miles. It never made the going into 1st gear issue any better. But the cold shifting was easier. I just changed to Redline lightweight Shockproof and it feels a tad smoother in all gears. But the 1st gear issue has not changed.
My friends 2002 WRX shifts just fine in every gear and he just changed to Redlines 75-90 weight GL5 gear oil from the stock fluid. He says it shifts just like before and he has never had the difficult getting into 1st gear issue ever.
It just goes to show that some trannies work well and some don't. Why? I don't know. Manufacturing tolerances? Bad batch of syncros? I have read that even some of the 03-04 WRX's have the same gear problems.
Next time I am going to drive as many WRX's I can till I find one that shifts good.
Cheers,
Greg Downing
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Old 09-05-2003, 05:41 PM   #15
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Quote:
Originally posted by avatarr
it might not be a bad idea but it seems that it would have to be with the 02/03 wrx's as they are the ones that seem to have the most complaints when using various synthetics.
Heh, it's because they're all former-Honda owners complaining that their trans' don't shift like their old cars. 98-99 RS's have horrible tendencies to grind 3rd and 5th, with much more frequency then the WRX's. Besides... they're all the same design transmissions, and the only differences are the gear ratios. *shrug*
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Old 09-18-2003, 07:59 PM   #16
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Well i recently changed to Neo synthetic 75-90 HD , the shifting is much smoother than before. And can shift into first a little big higher.

I overfilled it the first tiem and took a bit out today, ive bene getting a click -clank when I shift, like I can hear my syncros hitting each other.

Is this a good or bad thing? Some people say it my be too slick for my syncros. I took a bit of the stock oil and put it in(like a pint or so) I will try and report back in a week or so.
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Old 09-18-2003, 08:09 PM   #17
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Well after a 1000 miles with the Redline lightweight shockproof which I changed from the RL 75-90NS I can say that I am able to get into 1st a lot easier, I have had no grinds up to 10mph.
But 4th gear is more notchy and is finicky now. No grinding on the track up or down in 4th, just a hesitation it never had before.
Going into 2nd is much better when cold. 2nd cold used to feel like 4th feels now. 4th does smooth out some when the oil heats up.
It seems there is no perfect solution except to but a automatic tranny, Nooooooooooooooooo!
Greg D.
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Old 09-19-2003, 02:43 PM   #18
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I had all the typical problems. Then I switched to Amsoil series 2000 20w50. All problems are gone. No more grinding, easier to shift into 1st, all better.
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Old 09-21-2003, 08:58 AM   #19
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Wow, is 20w50 good for trannies? Never saw that light of weight oil being run in any tranny. I see you live in Wisconsin, which is cold, but why so light? Then again, I've heard of people running ATF as engine oil so nothing should surprise me anymore.

-Charles-
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Old 09-21-2003, 09:04 AM   #20
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Quote:
Originally posted by teiva-boy
I have tried 7590NS, royal purple, and Torco, in my car, and none can help my 2>1 shift.

I'm about to try Neo or some sort of lightweight oil perhaps soon. Ah heck who am I kidding, I want a new tranny!
Dont we all. Ive had good luck with neo others have not.
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Old 09-21-2003, 01:13 PM   #21
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Default Re: 20w50

Quote:
Originally posted by ImprezaVA
Wow, is 20w50 good for trannies? Never saw that light of weight oil being run in any tranny. I see you live in Wisconsin, which is cold, but why so light? Then again, I've heard of people running ATF as engine oil so nothing should surprise me anymore.

-Charles-
i thought the same thing when i read it. interesting indeed.

-Jason
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Old 09-21-2003, 03:31 PM   #22
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Ya it was shocking to me also. I was talking to my amsoil dealer about my tranny problems. Told him about the grinding and its not wanting shift smoothly.

So he told me that he runs 20w50 in his tranny(toyota paseo manual) and has had no problems. I was so sick of the grinding that I just did it, and it is just wonderful. It took about a week for the new fluid to disperse the older thicker stuff but during that time it kept getting better and then after a week it was great.

I would definately suggest trying it, and if you don't have the same results within a week I would be very suprised. I think the stock fluid is just too thick. I don't think it allows the blocking rings to engage properly and that's what is causing the grinding.

I have over 10k miles on my car with this fluid and it is fine. Over 92k miles on the car all together.
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Old 09-21-2003, 03:44 PM   #23
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20W50 engine oil is equivalent to about 80W90 gear oil. I just wonder about the friction modifiers since there are none I know of in engine oil.

See the chart --> http://www.nightrider.com/biketech/oilinfo1.htm
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Old 09-21-2003, 05:29 PM   #24
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well you learn something new every day


thanks.

-Jason
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Old 09-21-2003, 11:06 PM   #25
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No friction modifiers will mean that the synchros will grab better. Friction modifiers lower friction and is usually used for clutch based LSDs to reduce chatter.

That is probably why 20w50 motor oil works well in the transmission.

The problem is that motor oil will break down quickly in a transmission, you will need to change it far more regularly than a transmission fluid.
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