Gear oil performance? Take a look...

[MrTodd]

So I've been researching about different types of common gear oils, all in the 75w-90 weight for our transmissions, and I found a very interesting research article comparing a variety of oils available from the parts stores...

Check it out.

http://www.grattaoil.com/wh/A-Study-of- ... -Lubes.pdf



If the above link doesn't work, let me know! I have the PDF saved on my computer.

Anyway, in the end, I'm not saying that these are the best oils to use in our transmissions (as I'm new to Subarus, and I still have a lot to learn), but I think it will have me steer clear of a certain select few when it comes to refilling my differential and transmission. Now, I just wish I could see how Subaru's Extra-S formula compares!

Cheers.

[rallyak]

Nice read, maybe that why my transmission has been happy. I've been using amsoil severe gear for a few years with redline lightweight shock proof and haven't had any problems. It use to grind between 1st and 2nd a little after rebuild and changed oil after 500 miles to amsoil.

[MrTodd]

Nice!

Yeah, it is crazy how the Amsoil basically aced every test. Where did you end up buying yours? I'm starting to think I should use that on my wife's new WRX..

(EDIT: nevermind, I just now gave in and ordered directly from the Amsoil site)

[kimokalihi]

Well amsoil was the first with synthetics in automobiles. I tried that redline shockproof with motul 300 mix everybody swears by and it didn't help a bit. Switched to subaru extra s and no difference there either. I didn't read the article since it was 24 pages long. Maybe someday but ill try amsoil next. Just wish they'd make it more availavle locally.

[MrTodd]

Definitely check out the entire article when you have time! It's a thorough review of several different gear oils, pretty cool stuff.

I'm assuming the Amsoil actually would feel the best when shifting, but I only say that when looking at the viscosity index that the study provides. Other than that, the oil is only better in terms of durability and longetivity (in EVERY sense of those words, that is).

I just ordered 4 qts from the Amsoil website for my wife's 2014 WRX. I'm planning on putting 1/2 quart of Pennzoil synchromesh with it. For the rear diff, I'll just be using the Amsoil by itself. Anyway, Pennzoil Synchromesh has been shown to help promote smoother shifting in Hondas, and it's part of "scotty's" little cocktail mix that everyone at NASIOC seems to go ape shit over.

Either way, you'll have to let us know what you end up doing! I'm interested to find out. In the meantime, I'll be putting some Mobil 1 synthetic 75w-90 + Pennzoil synchromesh in my current '93 Legacy this weekend. I can tell the synchros are pretty beat up, as it doesn't shift very smoothly at all. I'll post my results after switching to that! Right now I'm just using the cheapest 80w-90 I could find at the parts store (Coastal brand), that said, I'm sure anything will feel better than that.



(EDIT: Darn. I'm starting to sound like an Amsoil rep. Sorry guys! I'm just getting excited about trying something new, that's all.)

[James614]

I went with Amsoil severe gear when I did my swap. Nothing to compare t to. My trans shifts like crap, but I dont know the life it led prior to my swap.

In general though, I use Amsoil oils and oil filter eveywhere that matters (not the rear diff because those will outlast the car regardless). With lubrication I go with the very best.

[kimokalihi]

The rear diff only outlasts the car when its full lol. I had one last about 100 miles once.

[James614]

I just read the entire thing. I feel like the service test at the end should have been done for all gear oils. We got to see that severe gear is good stuff, but its very difficult for us laymen to translate ATSM test results into real-world performance. Im betting Amsoil isnt the only one that would have displayed favorable wear in this test. The oils that failed some of the tests miserably are still popular and not known for causing premature drivetrain failure.

[Legacy777]

There is a reason Amsoil aced all the tests. Check out the bottom right corner on the first page:

AMSOIL Drivetrain Division
September 2007
AMSOIL INC.

This study was done and funded by Amsoil.....so of course their oil is going to do well

I'm not knocking Amsoil, but I don't know if I could say this test report is unbiased and independent.

The other thing to keep in mind with Subaru manual transmissions is that the gear oil is being asked to do two different tasks that require different properties. The first task is to lubricate the gears and provide "extreme pressure" protection for the hypoid gears. A very "slick" and slippery oil the provides low friction is beneficial for this task. The second task is to provide slight friction for the balk rings "syncros" so they can speed match properly. A very slippery gear oil does not perform this task very well. Which is why you can see more gear "grinding" with synthetic than you do with conventional gear oil.

Because of these polar opposite requirements in a Subaru transmission I think that's why Subaru developed their own gear oil.

I've run a variety of synthetic and convential gear oil over the years to try and find the "magic" one, but have been happy with Subaru's Xtra-S trans gear oil.

[MrTodd]

Good to read all the insight from everyone.

I'm very well aware of how synchros work, as I've rebuilt 2 transmissions so far. In fact, the friction aspect of things is very much the same concept on how helical LSD's work. That said, you'll notice that many of the synthetics state that they have something like 'friction modifiers' added to help reduce things like overall LSD performance and chatter. This modifier can also be beneficial on synchro operation. I installed an LSD in my last car, and I actually ended up using conventional oil in the transmission. However, my last car also stated to use a substantially lighter weight oil than 90 weight gear oil - it called for 30 weight motor oil. Thus is beauty of Subaru deciding to actually use a gear oil in their transmissions, you get oil that was specifically designed to operate both to prevent high load gear wear, smooth long lasting bearing operation with minimal shearing, and lastly, synchro performance.

That being said, Subaru's have a much better selection in oils than other cars that use lighter weight, motor oil as their transmission oils, as they are application specific. The real problem with transmission fluids is in that case: when a manufacturer calls for 30 or 40 weight engine oil in their transmission. THAT is where you get a conflict of interest, as motor oils are primarily designed for film strength, low viscosity, and the ability to provide the least amount of friction possible on all surfaces. This is detrimental to synchro operation, to a certain extent. Gear oils, on the other hand, are designed either for simple differential operation, or full on transmission operation. Thus, you get oils that are actually designed to work with what they're being put in (ie synchro performance AND gear/bearing protection). I'm sure Extra-S is fantastic, but I really don't think it's THE BEST 'doesn't matter what you think, nothing else can compare' type of oil out there for transmissions.

Even so, I didn't read at the very bottom that this test was done by Amsoil themselves. Still, I'm thinking it may be good info regardless. The testing procedures are well documented, many of the results are pictured. Yes, it certainly could be all a complete lie, but that would be a bit silly for an oil company to do such a thing; they'd much more likely just make stupid claims with no supporting evidence, like Royal Purple always does..

[MrTodd]

Okay, so I went ahead and changed my own transmission fluid on the Legacy. My wife's WRX is still on OEM fluid.

This is what I went with: 4 quarts of Mobil 1 Synthetic 75w-90, along with Pennzoil Synchromesh...




Filled the rear differential with straight Mobil 1. Filled the tranny with 3.2 quarts of Mobil 1, then exactly 1/2 quart of Pennzoil Synchromesh - a total of 3.7 quarts in the tranny.

Drove the car around for about 30 minutes.... Let me tell you, shifting feels SUBSTANTIALLY better. Now, keep in mind, I was using the cheapest (ie Coastal) 80w-90 gear oil in the parts store before this fluid change; that said, I'm sure anything would've felt better. Even so, I must say that I'm very impressed with the improvement of my shifter feel. Don't get me wrong, it's no racecar transformation, but for what I use it for (mostly city driving), it's working MUCH MUCH better.

I'm not saying everyone should go try this, or that it is some magic recipe that is the end-all, cure-all rally fix that is better than everything else out there. Instead, I'm just stating my results, and this may be a decent combo if you're unsure of what to put in there.

Hope this helps.

[Legacy777]

My comments are mainly from my personal experience and direct experience of others. So like anything on the internet, everyone is free to make up their own minds The Xtra-S provides the best balance of cost, performance, and protection that I've run across in terms of how a Subaru transmission shifts and performs. Is it the "best", maybe not, but it is probably one of the best when you take price point and availability in mind.

Also just to clarify, helical LSD's are torque sensing LSD's and typically use gearing to accomplish the limited slip capabilities. The friction modifiers are typically beneficial for clutch type LSD's.


Also, here are some pics of the Uncle Scotty Cocktail. The main thing you'll see is that the fluid separates when it sits. Again, from my personal experience and direct experience of others, I don't recommend running it in Subaru transmissions. This thread has a lot more info as well:

http://www.bbs.legacycentral.org/viewto ... 16&t=27436

http://main.experiencetherave.com/subar ... /cocktail/
http://main.experiencetherave.com/subar ... cocktail2/

[James614]

I myself would use Extra-S if there was a convenient local source for it. Not only is the nearest dealer 15 miles away, they are run by Toyota crooks who know nothing about Subarus (I tried to get crossmember bolts from them one time and they tried to tell me the bolts for virtually all pre2000s Subarus are discontinued and they didnt have a way to look up superceded part numbers) and employ the worst in high pressure sales tactics every time step foot on their property. I know I can order the drums online but thats a pain and a half. Since Amsoil's stuff is available at Carquest, thats what I use as I know Amsoil makes a good oil.

[Legacy777]

You can buy quarts of Xtra-S on amazon.

http://www.amazon.com/Subaru-75W90-Extr ... B007L6Q1EK

[James614]

Good old Amazon, always secretly havingreally handy stuff that youd never think to look there for. But $20/quart?! Im willing to give it a try but damn I thought the Amsoil was expensive at $13/qt

[Legacy777]

Yeah, it's not cheap....and probably cheaper to get the drum.

[Legacy777]

Here's some that is MUCH cheaper

http://www.fredbeansparts.com/subaru-75 ... ottle.html

[MrTodd]

Helical LSD's use friction for the torque bias. The sides of the spur and worm gears actually press/rub against the differential housing and each other for the transfer of power. This was actually something I recently learned.

Take a look at this video, along with the links he provides in the description. I have no idea how the inventor thought of this thing....


Torsen LSD - Torque Transfer - Explained: http://youtu.be/lDsQAs0Ldes


Considering the above, friction modifiers are beneficial for helical LSD's.

[MrTodd]

But all of what I'm saying is really a moot point.. Fact is, you've got a lot more experience than me with Subaru transmissions.

In addition to that, the link you posted for the extra-s is actually a really good deal even if it were some other type of fluid! I'm starting to consider using that instead of the Amsoil in my wife's car..

[James614]

Yeah, my next change will DEFINITELY be extra S now.

If you think about the uniqueness of our application, it makes a lot more sense to use Extra-S compared to other Subaru fluids. Not saying Subaru fluids arent good, but I have a feeling their coolant and motor oil cant claim all the same advantages in their much more generic applications.

[kimokalihi]

Good old Amazon, always secretly havingreally handy stuff that youd never think to look there for. But $20/quart?! Im willing to give it a try but damn I thought the Amsoil was expensive at $13/qt

Amazon is the first place I look when buying anything but groceries. Amazon prime ftw!

[MrTodd]

Amazon is the first place I look when buying anything but groceries. Amazon prime ftw!

I'm right there with ya. I remember a long time ago when I was looking for oxygen sensors for my last civic, all the prices I was finding were ridiculous. Then checked Amazon, an OEM NTK sensor was like $25, new. Haha. Solid deals for sure!

[Legacy777]

Helical LSD's use friction for the torque bias. The sides of the spur and worm gears actually press/rub against the differential housing and each other for the transfer of power. This was actually something I recently learned.

Take a look at this video, along with the links he provides in the description. I have no idea how the inventor thought of this thing....


Torsen LSD - Torque Transfer - Explained: http://youtu.be/lDsQAs0Ldes


Considering the above, friction modifiers are beneficial for helical LSD's.

Thanks for sharing that video it is helpful in understanding Torsen LSD's (I learned a little more). However, I still say friction modifiers are not necessary for helical LSD's. They can affect the amount of lock up, but are not necessary.

Here is a thread on bob is the oil guy talking about it.

http://www.bobistheoilguy.com/forums/ub ... ber=501472

[MrTodd]

Thanks for sharing that video it is helpful in understanding Torsen LSD's (I learned a little more). However, I still say friction modifiers are not necessary for helical LSD's. They can affect the amount of lock up, but are not necessary.

Here is a thread on bob is the oil guy talking about it.

http://www.bobistheoilguy.com/forums/ub ... ber=501472

Thanks for the clarification! This is very good information, looks like my ideas are incorrect. *Foot has now been inserted in mouth*


EDIT: Oh BTW, considering I already ordered in the Amsoil for my wife's WRX, I figure I'll just put it in to see if there is any difference (good or bad) in terms of shifter feel. If things feel worse, I'll order some Extra-S right away and replace it with that. If it feels alright, I'll keep it in there for the time being, although the next fluid change may just end up being Extra-S anyway. I say this because the amazon link you posted has such a solid deal! Thanks again for that. In the meantime, the Mobil + Pennzoil combo is still working quite well in my Legacy. I figure I'll keep that in there, as I don't have any real performance aspirations in mind with it. Even so, it seems to be a good bang-for-your-buck combo.

[208ss]

i run Smurf blood in my transmission . redline shockproof . But I also have ppg gears.