Subaru STi Syncro/Gear oil Conundrum!

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Originally Posted By: MolaKule
When you have a hypoid differential using the same fluid as the tranny, you are forcing the transmission to shift in a fluid that is not optimum. That is, it is difficult to make a fluid to have the GL-5 protection properties for differentials and at the same time provide some measure of friction modification to the transmission.

This is the reason behind using Subaru's own Extra-S and being done with it.
 
I don't think it's that simple. From what I understand, extra-s is just the OEM factory fill for the STI, that's it and that's all. Dealerships probably don't use that fluid when they do transmission or diff services on any subaru, even if they're supposed to. I'd like to think that extra-s is a magic fluid that somehow satisfies the transmission and front diff, but there really isn't much evidence to support this in my opinion. As far as I know, it's just another GL-5 fluid with a lot of good reviews, but also some negative and neutral reviews.
 
While I generally agree with you for the most part, Subaru must have their own recipe that's different enough or has just enough additives to satisfy everything to make it worth producing.

That said, there are some other lubes that work 'well enough' in the Subaru transaxle for 98% of the owners out there so I'm sure that why the dealership doesn't care what they use as long as they can get it in bulk. It's a lot harder to sell a transmission and diff service when 'real' Subaru lube is $15 a quart and generic 75w90 GL-5 from their supplier is only $5. Remember, dealerships are in it for themselves so I wouldn't use them as an example of what is really correct, only what is good enough.

And I'm not knocking Motul 300, either. I'm sure it's fantastic stuff in other applications but the Subaru transaxle is picky.
 
Despite what I said earlier I do agree with you. Extra-S is probably one of the better, if not the best option for a Subaru manual gearbox that calls for a GF-5 fluid. I'm actually planning on changing the manual transmission fluid in my subaru soon, and I am totally up in the air on what to use. Right now it's between supertech semi-syn 75w-90, redline 75w-90NS, and extra-s, we'll see.
 
Originally Posted By: MolaKule
Quote:
You just said the Motul was likely too slippery and the Pennzoil added a sufficient amount of friction modifier. Which is what I just got done saying. In fact I've already tried it and it worked to some extent...


No I was disagreeing with you. The Motul has an excellent base oil with a close viscosity and but it does not have the friction modification necessary for manual synchromesh transmissions.



I disagree Mola, it is optimised for MTF use with apparently the right FM's and works very well as a manual gearbox lube, it just has an EP treat rate for transaxle hypoid diff use too.

It's very similar in performance to Castrol Syntrax http://www.castrol.com/liveassets/bp_int...90_B1278983.pdf which was originally brewed for TWR Jaguar's XJ220 transaxle, the big difference is that Motul Gear 300 is much better at lower ambients as its VI is 222, yet doesn't appear to shear much in use.

I'm pretty enamoured with it
laugh.gif


[edit] Put it this way, Gear 300 shifts as well as a Castrol Syntrans 75W-85 GL4 in a Land Rover R380 gearbox (and better/more consistent at elevated temps/loads) and both fluids were better than Torco RTF.
Syntans 75W-85 is considered the fluid by most that have experimented for the Landy R380 g/box here in Oz, and Castrol Syntrax 75W-90 was at least as good in shifting performance when I backed to back it against Redline MT90 in a Nissan Patrol g/box.

The Landy g/box now has 304,000km on it (but only about 20,000km with Gear 300) and the Patrol has 420,000km on it, 315,000km of that on Syntrax. (during the warranty period was the Nissan Factory fill, then Fuchs Titan 75w-90 an 2000km in between on MT90)
 
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I should've said "optimised as best you can with a GL5 EP add package"

I'm not sure what they use for the EP add pack, can't recall it having a strong sulphur smell (??) and the high VI has me intrigued, perhaps the same or similar VII's to what Castrol Europe are using as it definitely doesn't shear as readily as some other full syn MTF's I've used ?
 
Originally Posted By: Bottom_Feeder
While I generally agree with you for the most part, Subaru must have their own recipe that's different enough or has just enough additives to satisfy everything to make it worth producing.

That said, there are some other lubes that work 'well enough' in the Subaru transaxle for 98% of the owners out there so I'm sure that why the dealership doesn't care what they use as long as they can get it in bulk. It's a lot harder to sell a transmission and diff service when 'real' Subaru lube is $15 a quart and generic 75w90 GL-5 from their supplier is only $5. Remember, dealerships are in it for themselves so I wouldn't use them as an example of what is really correct, only what is good enough.

And I'm not knocking Motul 300, either. I'm sure it's fantastic stuff in other applications but the Subaru transaxle is picky.


I'm not sure I follow. Motul Gear 300 is probably one of the best fluids for this application, depending on the purpose of the car. Were this a Civic MT and the goal was 1,000,000 miles, then swapping from the appropriate fluid to something like Motul Gear 300 would be a waste of money and more than likely cause issues for which the is no positive tradeoff.

With the STI front LSD, using something that's GL-4/5 compatible will promote long gear life at the expense of some cold shifting. However, the deleterious affect on cold shifting may not even be true, since Subaru's Go Extra S, Motul Gear 300 and now Redline's NS formulas all have produced similar shifting during cold weather. I just swapped out the Gear 300 for the Redline lube, so I won't know how it reacts (if any differently) in warmer weather.

So, my end point with respect to the OP, is that a better gear oil is prefered for aggressive driving over a better MT lube in this application, and IMO. If the synchros are worn out (either due to defect or too many non-rev-matched shifts,) then that's a mechanical issue, and not the fault of the lube itself. It may be that using a different lube with fewer or no friction modifiers will act as a Bandaid, but it's not going to fix the problem.

One thing I don't know, and would love to hear more from MolaKule on, is how a true GL-5 gear oil will affect synchro life. Motul Gear 300 is dual-rated and definitely doesn't smell as nasty as any of the other gear oils I've used thus far, if memory serves me correctly. If there is only a moderate amount more potential for corrosion, then the GL-5's protection will be worth the risk, IMO, because rev matching and other methods to preclude excessive operator-induced wear are possible.

On that note, what's the correlation between synchro failure and operator vs corrosion (due to lube choice) induced degradation?
 
I put Motul Gear 300 75W90 in my Subaru 5 speed manual last fall, and I liked its ease of shifting on a 15 degF winter morning. The next test is how it performs on a 95 degF summer day.

Those who promote the Gear 300: Lightweight Shockproof cocktail assert that the Redline Shockproof protects the hypoid gear set and has favorable friction characteristics for the Subaru synchronizers.
 
Well, to update I guess..

Synchro still stubborn. In the morning I have to fight to get into reverse or first. Warmer weather hasn't helped me any.


On a weird side note, my front diff (posi) is locking up way more than before. On blacktop when I turn I can hear the tires trying to turn at the same speed (inner tire squeak etc) and when doing a sharp turn out of my driveway my car kinda walks like an old 4x4 truck. Only when doing real sharp turns on blacktop.

Which these cars are known for doing! BUT.. When running Motul 300 only, it never acted like this...



Idk.. I just need to try redline or some cheap dino oil.

Any recomendations for a oil that would be CHEAP, and good for SYNCHROS??
 
Could try supertech synthetic blend 75w-90 from walmart, only $5 per quart. It worked pretty well in my MT legacy, except it did grind if I tried to shift really fast, which I didn't do often.

Supertech Pictures
http://img440.imageshack.us/img440/9358/lube.jpg
http://i465.photobucket.com/albums/rr12/Ripsaw_1088/11-16-09004.jpg

I just picked up some Red Line 75w-90NS that I plan to put in soon, I've read mixed reviews about it so I wanted to give it a try.

*I'm doing some reading at nasioc, and people are saying good things about 3 quarts of RL 75w-90NS, and 1 quart of RL shockproof, I assume the 75w-90 shockproof? People are also saying to shift from N - 2nd - 1st (or R) to get the car to go into first gear smoother/faster, but I know this is a hassle.
 
What is the yellow metal rating of the Subaru oil? Some GL-5s are not safe, but many are. As long as it is rated A1 or A2, it's fine for brass alloy syncros and won't corrode them.

The subi boxes have a weird feel to them compared to a Honda or something, but I think PROTECTION is much more important than shift feel or speed.

Your posi is probably locking up more now because you used pen synchromesh, a fluid with additives that increases friction. This is not what your posi needs to operate properly.

I don't think I could buy an auto subi but at least they have a separate front differential from the trans.
 
Just wanted to throw a few things out there after switching to Red Line 75w-90NS from Supertech synthetic blend 75w-90 in my 2009 subaru legacy which has a common sump.

For the first 1-2 days with red line, the car seemed to require more effort to change gears. Also, one of my previous "complaints" was that when I tried to shift too fast with supertech, the gearbox would grind. For the first 1-2 days with red line, I couldn't shift that fast even if I wanted to, the RL seemed to slow down shifting quite a bit. The car also seemed to bog a bit when I would want to start going after shifting from reverse to 1st. I don't think the gear oil could've caused this, but it was just something I noticed after changing the fluid. The weather in Connecticut has finally started warming up, so I just figured that my ecu might be adjusting to the warmer weather.

Fast forward a few days. The car now shifts much, much smoother, and I can shift the car very quickly now if I want to.

I guess I just wanted to throw this out there because I'm confused. For the first 1-2 days, I completely regretted switching to red line because of the increased effort to shift. But now the car shifts fine, I don't understand why the car acted that way for 1-2 days. The weather has been the same here, so I can't blame temperature change. I was also a bit nervous because a fellow legacy owner said that when he switched to RL NS, his car shifted great for the first 3k, then it started to grind, and after 20k the transmission was blown. I don't understand how a good GL-5 fluid like red line NS could cause that to happen, but I don't know a whole lot about transmissions. Thoughts on anything I've said?
Subaru lists their manual transmission fluid recommendations below
2009legacy5mtfluid.jpg
 
Originally Posted By: sxg6

For the first 1-2 days with red line, the car seemed to require more effort to change gears. Also, one of my previous "complaints" was that when I tried to shift too fast with supertech, the gearbox would grind. For the first 1-2 days with red line, I couldn't shift that fast even if I wanted to, the RL seemed to slow down shifting quite a bit. The car also seemed to bog a bit when I would want to start going after shifting from reverse to 1st. I don't think the gear oil could've caused this, but it was just something I noticed after changing the fluid. The weather in Connecticut has finally started warming up, so I just figured that my ecu might be adjusting to the warmer weather.

Fast forward a few days. The car now shifts much, much smoother, and I can shift the car very quickly now if I want to.

I guess I just wanted to throw this out there because I'm confused. For the first 1-2 days, I completely regretted switching to red line because of the increased effort to shift. But now the car shifts fine, I don't understand why the car acted that way for 1-2 days.
[snip]


The new FM's take a little while to flush or 'lift' the old ones out and bed into the synchro clutch faces, it can take anything from ten minutes to 800km or so for this to happen.

I've had this exact thing happen a few times, once when first using Torco RTF every single upchange crashed and crunched, then after three days shifting became normal.
 
Subaru calls for brake fluid to be used as clutch fluid. Oddly enough they say DOT3 and DOT4, but don't list DOT5? The same is true for my 2009 subaru, dot3 or dot4. I know very little about brake fluid, and even after doing a little reading (link below) I don't know why subaru doesn't list dot5. Any ideas?

http://www.stoptech.com/technical-support/technical-white-papers/brake-fluid

2004 STI recommended fluids below
 
Originally Posted By: sxg6
Subaru calls for brake fluid to be used as clutch fluid. Oddly enough they say DOT3 and DOT4, but don't list DOT5? The same is true for my 2009 subaru, dot3 or dot4. I know very little about brake fluid, and even after doing a little reading (link below) I don't know why subaru doesn't list dot5. Any ideas?

http://www.stoptech.com/technical-support/technical-white-papers/brake-fluid

2004 STI recommended fluids below



DOT 5 is silicon (non hygroscopic but compressible, don't use in high performance applications)

DOT 5.1 is high performance (very high BP) glycol ether or borate ester (conventional) brake fluid.
 
Quote:
I disagree Mola, it is optimised for MTF use with apparently the right FM's and works very well as a manual gearbox lube, it just has an EP treat rate for transaxle hypoid diff use too.



Not according to the OP's original comments and lack of data.
 
Being a 22 year mechanic and a Subaru only specialist since 2005 and use Amsoil, I have found a mix that works extremely well.

Total fill is 4.35 qts. I use 3 qts. of Amsoil FGR, and the remaining 1.35qt. I use Amsoil MTF.

Subaru chose to use a fluid that protects the gear teeth over the synchros. ( and the limited slip diffs IMHO )

When you do the job, pull the pan and clean the magnet that is mounted directly above the pan. Use RTV GREY to reseal the pan,follow the RTV instructions to the letter and tighten in a criss cross pattern to proper torque spec of 4.7 ft. lbs.

I hope this helps, I have used this combo in over 200 STi's

Flat foot shifting is not an issue, going from neutral to reverse is not an issue, cold weather is not an issue at all.

For some extra info, Severe Gear 75-110 is exceptional in the rear diff. I personally use Redline D4 in the power steering and it has doubled the fluid life and is very smooth.

If I remember correctly, Extra-s comes 5 gallons at a time as well.
 
Quote:
Being a 22 year mechanic and a Subaru only specialist since 2005 and use Amsoil, I have found a mix that works extremely well.

Total fill is 4.35 qts. I use 3 qts. of Amsoil FGR, and the remaining 1.35qt. I use Amsoil MTF.



That makes sense.

I spoke today with the Master Mechanic at my Nissan/Subaru dealer and he said if they have customer shifting complaint issues with the Motul 300 they use Redline 75W90 GL-5 Gear Oil and Redline MTL 70W80 in about the same 3:1 proportions.

He wants me to come up with a "one-oil" solution so he doesn't have to mix. HMMM!
 
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