Change your manual transmission fluid ASAP!!!

[qqzj]

Thanks for the discussion. 2 questions.

1. Do you think Motul Gear 300 gear oil is a good oil for the differential?
2. Which MTF would you recommend?

Thanks a lot.

Originally Posted by Resolute

Yes, Gear 300 is both GL-4 and GL-5, but a lubricant meeting both the GL-4 and GL-5 specifications is not necessarily suitable (much less better) for use in a transmission requiring GL-3 or GL-4 gear oil.

The GL-5 specification was created to establish a gear oil whose chemistry is better suited to handling the severe sliding and loading conditions imposed by hypoid gear mechanisms than GL-4 lubricants. To do so, GL-5 gear oils must have higher concentrations of extreme pressure (EP) and anti-wear additives than GL-4 oils. So, by design, a GL-5 gear oil can also be labeled as meeting the GL-4 requirement with the amount of EP additives it contains, in much the same way that a 93 octane fuel will 'meet' the lower anti-knock specifications of a 91 octane rated fuel. But they are not backwards compatible. In other words, while a GL-5 oil exceeds the GL-4 EP requirements, a GL-4 oil does not have enough EP additives or anti-wear characteristics to satisfy the GL-5 specification.

The extreme pressure (EP) additives used to meet the GL-5 oil standard must chemically alter (corrode) the gear surfaces in order to establish a film strong enough to withstand the high pressures of the gear loads and also not be removed by heat and friction. Most EP additives are composed of sulfur, phosphorous and chlorine compounds because of their ability to bond with and chemically alter steel surfaces. When these compounds corrode the surface of softer metals such as brass or copper, they can be removed from the softer native metal by friction. This leaves softer metals looking pitted. Hence, the old scare that GL-5 gear oils will destroy brass synchros in a transmission. This is really not a huge issue for most gear oils though, GL-5 or otherwise, since modern gear oils typically contain buffer compounds that prevent EP additives from bonding with and corroding the surfaces of softer metals. If it's spec'd for manual gearboxes, GL-5 or otherwise, you shouldn't have an issue with pitting soft metals.

The real problem with GL-5 oils in a transmission is that the EP additives also reduce the sliding friction across the reacted surfaces. This is normally a good thing, but the synchronizers in a manual transmission require friction to operate. When you use your shift lever to slide a synchronizer ring (spinning at the same speed as your input shaft) into a selected drive gear (spinning at a different speed), friction is what transfers the energy from the synchronizer to the selected gear and brings it up (or down) to speed. Once the rotating speed of the gear matches the synchronizer, then the locking ring on the synchro can slide over and lock into the drive gear, completing the shift. How long this process takes is directly impacted by the rate of frictional energy transfer. Oils which meet the GL-5 specification will slow this energy transfer down because they reduce friction across the reacted gear surfaces.

Manual transmissions that spec a GL-4 oil (or even a GL-3 oil for our cars), are specifying a gear oil with lower amounts of EP and anti-wear characteristics in order to improve synchronizer operation. This is a pretty common practice for manufacturers whose manual transmissions do not contain hypoid gears Manual transaxles tend to specify a GL-5 because gear protection trumps shift feel in that application.

I have typically found GL-5 gear oils in manual transmissions to have worse synchro performance than GL-3 or GL-4 oils, hence my surprise that so many here seem to prefer it. I wonder how much of that preference really comes down to advertising and having the Motul name on the bottle.

[Resolute]

Originally Posted by qqzj

Thanks for the discussion. 2 questions.

1. Do you think Motul Gear 300 gear oil is a good oil for the differential?
2. Which MTF would you recommend?

Thanks a lot.

1. It is a great gear oil.
2. I don't have any experience using different MT fluids in this car to recommend one over the other.

My post was intended to simply highlight the principal difference between GL-4 and GL-5 gear oils, provide some clarity on the issue of gear oils and yellow metals, and to explain my surprise that so many seem to prefer a GL-5 oil, since my experience with other manual transmissions supports the choice of many manufacturers to specify a gear oil with lower amounts of EP and FM additives (GL-3 or GL-4) than a GL-5 gear oil in order to promote synchro operation and shift feel. It wasn't meant to imply any personal recommendations for or against a specific oil in this transmission.

[ZionsWrath]

Any opinion on Mobil Delvac?

[Antihero983]

Just a quick comment:

As a dealer tech, most of the cars I see that come in with 30k and under that get their manual transmissions, or even front diffs drained and filled have super dark fluid. I wonder if its just the stuff they're putting in at the port is garbage.

[qqzj]

Besides Motul, the other desirable MTF is Pentosin MTF2. But that oil has slightly less viscosity. So I am kind of conflicted. Don't know which one to use.

Originally Posted by Resolute

1. It is a great gear oil.
2. I don't have any experience using different MT fluids in this car to recommend one over the other.

My post was intended to simply highlight the principal difference between GL-4 and GL-5 gear oils, provide some clarity on the issue of gear oils and yellow metals, and to explain my surprise that so many seem to prefer a GL-5 oil, since my experience with other manual transmissions supports the choice of many manufacturers to specify a gear oil with lower amounts of EP and FM additives (GL-3 or GL-4) than a GL-5 gear oil in order to promote synchro operation and shift feel. It wasn't meant to imply any personal recommendations for or against a specific oil in this transmission.

[504]

I've tried ALL the high end 100% synthetic fluids (yes I have binned 500 dollars plus). Stock fluid was amazing, it was my first manual tranny and naturally thought I could improve with fresh stuff to get rid of break in material. Oh was i wrong. Redline anything (I tried my alone, mt90) felt like death. Honestly running no fluid would've been better, second gear crunched almost every hit and got to the point I avoided driving

I stepped upto amsoil synchromesh and it was better, still Grindy on second, added 1 quart amsoil mt90 and that improved nothing.

Next up a fresh dose of gear 300 by motul, I remember it being similar to amsoil

Finally pentosin mtf2 and is so far the best. My second never grinds anymore but sometimes difficult or clanky. It's definitely the best of the fluids and becomes butter when you push the car.

I don't know anymore, maybe synchros damaged alittle after redline but I have driven my friends 86 which is older than mine as well as a brand new one and both feel butter in any condition on stock fluid.

*Sigh* try to do something good and you get yourself into a hole

[ZZT86]

For me stock fluid was shite but then again I wasn't convinced clutch pushrod was properly adjusted. Have also tried Gear 300 & felt similar as stock. Currently use MTF2 which I have plenty of here & just as well I do cos I ain't moving away from it as I reckon it's the best thus far.

You could also always go back to stock fluid, pretty sure available in 20L drums from Japan.

[SubaruLifer]

I thought the stock fluid was decent; I didn't have nearly the problems that everyone else here seemed to have. I switched to Motul Gear 300 in the trans & diff at about 30K miles, and I don't like it at all for the trans. I'll be looking at either trying Pentosin MTF2 or just going back to the OEM fluid when I flush it again next spring.

[qqzj]

But we do not know what OEM fluid really is and where to get it.

Originally Posted by SubaruLifer

I thought the stock fluid was decent; I didn't have nearly the problems that everyone else here seemed to have. I switched to Motul Gear 300 in the trans & diff at about 30K miles, and I don't like it at all for the trans. I'll be looking at either trying Pentosin MTF2 or just going back to the OEM fluid when I flush it again next spring.

[sato]

Originally Posted by qqzj

But we do not know what OEM fluid really is and where to get it.

Exactly... My dealer used some Valvoline stuff instead if any OEM fluids. The Toyota stuff documented in the manual (TOYOTA Genuine MG*Gear Oil*special II) is hard to find... Dealer probably opts for cheaper stuff compliant with the 75w90 and GL spec requirement.

Sent from my E6653 using Tapatalk

[ZionsWrath]

Originally Posted by sato

Exactly... My dealer used some Valvoline stuff instead if any OEM fluids. The Toyota stuff documented in the manual (TOYOTA Genuine MG*Gear Oil*special II) is hard to find... Dealer probably opts for cheaper stuff compliant with the 75w90 and GL spec requirement.

Sent from my E6653 using Tapatalk

WHen I first got the car I heard all over forum posts "Subaru Extra S". I asked local dealers they had no idea WTF I was talking about. I ended up finding a dealer online that sold it. So I ordered 8 bottles. But it came in just unmarked bottles so who knows it is probably just whatever they buy in bulk anyway.

I ended up going with motul. My trans is notchy but at high rpm on track its smooth. I'd be interested in trying something else in the MT but not sure what.

[SubaruLifer]

Originally Posted by qqzj

But we do not know what OEM fluid really is and where to get it.

Originally Posted by sato

Exactly... My dealer used some Valvoline stuff instead if any OEM fluids. The Toyota stuff documented in the manual (TOYOTA Genuine MG*Gear Oil*special II) is hard to find... Dealer probably opts for cheaper stuff compliant with the 75w90 and GL spec requirement.

Sent from my E6653 using Tapatalk

Originally Posted by ZionsWrath

WHen I first got the car I heard all over forum posts "Subaru Extra S". I asked local dealers they had no idea WTF I was talking about. I ended up finding a dealer online that sold it. So I ordered 8 bottles. But it came in just unmarked bottles so who knows it is probably just whatever they buy in bulk anyway.

I ended up going with motul. My trans is notchy but at high rpm on track its smooth. I'd be interested in trying something else in the MT but not sure what.

You guys all mean this stuff, right? http://www.fastwrx.com/products/suba...ance-gear-lube

FT-86 SpeedFactory also sells it: http://www.ft86speedfactory.com/suba...l#.V0dG0_krL4Y

[qqzj]

on the bottle, it is not mentioned this would be MTF. I know the 2nd website says so, but it is not on the bottle.

[LastRep]

Just fill until it starts leaking out the fill plug?