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Change To Syn Gear Oil Now!

73K views 268 replies 95 participants last post by  markthomas1969 
#1 ·
Lots of people mention the subject, but maybe it needs it's own thread.

Change your gear oil to synthetic as soon as you can. I used Mobil 1. One gentleman (he inspired me) used Redline. It might be better but its hard to find, here.

Keep the car level (no ramps, you can reach the drain) and drain every drop of the old oil. Mine only has a few K miles on it. Since my car is lowered, I needed my skinny son to get at the drain plug. Don't lose the washer!

You'll need a long a$$ funnel. Then dump in that Mobil 1.

I think the owners' manual is wrong in the capacity. It calls for 3.75 quarts. I used 4.

Then go for a drive and be prepared for a seriously dramatic change in your shifting and transmission behavior. It's hard to believe it's the same machine.

Go figure.

:) :)
 
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#104 ·
I was doing some research into the difference in gl-4 and gl5 rated tranny oils. It seems the gl-4 is designed for antiwear purposes and is well suited for production cars. The gl-4 rated oil is stable to around 200F and can handle moderate pressures (pressure between meshing gears ect). The gl-5 rated oil is used for higher end applications such as racing. The additives used to increase its pressure rating and shock tolerance are sulfer phospherus compounds. These compounds can attack/corrode yellow metals such as brass.

Does anyone know if the WRX synchros are brass? If they are gl-5 rated oils will shorten their life.

Here is a shamelessly stolen decription :)

___________________________________________________
What happens if API GL-5 gear oil is used in an API GL-4 gear oil application... ?
API GL-4 and API GL-5 products typically use the same extreme pressure (EP) additive system, with the API GL-5 having about twice the concentration of a API GL-4. In service, these additives become active under extreme load and temperature when the protective oil film can be squeezed away. EP additives work by forming wear-resistant compounds with the metal of the gear tooth surface. As the gears mesh, these compounds shield the gear teeth from direct metal-to-metal contact that would cause wear and damage to the gears. If too little of the active additive is present, proper protection would be compromised. Too much of this additive could cause excessive chemical corrosion of the gear surface. If an API GL-5 gear oil is used in a application where API GL-4 gear oil is called for, chemical corrosion of "yellow metal" components may occur, such as bronze synchronizers, brass bushings, etc. This may lead to shifting difficulties or shortened equipment life.
:)
 
#105 · (Edited)
Subaru recommends GL-5 fluid in our trannys. Maybe GL-4 fluid is too 'thin' and won't provide enough protection in the long run :confused:

Here is dome more info I have tracked down

From http://www.subarustore.com/redmtmantran.html
GEAR AND SYNCHRONIZER WEAR PROTECTION 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
 
#106 ·
the link you posted is for a aftermarket subaru vendor. I would not consider this to be a "recomendation" from subaru. The redline oil is the same description from the redline site.

just my 0.02

If anyone knows what material our synchros are made of this will answer the question.
 
#107 · (Edited)
squeeler said:
the link you posted is for a aftermarket subaru vendor. I would not consider this to be a "recomendation" from subaru. The redline oil is the same description from the redline site.

just my 0.02

If anyone knows what material our synchros are made of this will answer the question.
GL-5 is recommended in the owners manual, page 11-24 and 11-25 :D

As for the link and description, I was just trying to help point out some of the differences between GL-4 and GL-5 fluids. Sorry for the confusion ;)
 
#112 ·
The Synchromesh is still performing beautifully. The tranny seems to get smoother the longer I have the fluid in. I have no grinding noise at all no matter how fast I shift or at what RPM I shift.

Unfortunately, now I'm starting to develop the infamous clutch shudder. I just had a new clutch installed last year by Subaru because of the infamous clutch decel noise. I wish they could get these clutch problems straightened out in this car. I'm thinking about just installing a racing clutch since I'm eventually going to need one anyway.

Spend the $10/quart for the Synchromesh, you won't regret it.
 
#115 · (Edited)
I figured if it's good enough to hold a GM tranny together then it must be pretty good stuff. This is the fourth fluid that I have tried in the tranny. Others have improved the grinding slightly, but the Synchromesh has totally eliminated it. It has also made it easier getting the car in first gear while coasting to a stop. My car had to be almost at a dead stop before it would go into first gear but now it slides in sooner and easier with the Synchromesh.
 
#117 ·
Flyboy said:
I figured if it's good enough to hold a GM tranny together then it must be pretty good stuff.
LMAO!
 
#118 ·
Cmon now GV27! I'm making poopy unhappy faces now. GM autoboxes frag with almost the regularity of Ford slushboxes, But their manual transaxles are pretty darn reliable.

I'll give GM credit for not engineering their transaxles to within an inch of their life like Subaru has with the REX. The fragility of our gearboxes is imho, unexcuseable.

Are you some kind of GM hater? omg!.... <----- massive sarcasm

j.p.
 
#122 ·
btw, folks, i "topped off" my MT fluid with a few OUNCES of synchromesh fluid and it made a difference. i didn't have much of a problem but the occasional clatter going into 1st on a roll. now i've been experiencing a little faster mesh upshifting, and 1st gear has been quiet.

in other words, you may be able to get by with a blend instead of going whole hog. this may assuage some fears about gl4 vs gl5 and lubrication.

the rest of the fluid is OEM at this point.

jm2c and another data point,
ken gilbert
 
#123 ·
Tried the mobil 1 synthetic, Transmission was way smooth, but I got a grind when shifting from 3rd to 4th (driving hard). Changed that out and put Redline MT 90 and it is just as good plus no grind. It even goes into 1st better. This is the cheapest place I found for it ttp://www.pitstopusa.com/REDLINEGEAROILATF.asp And that is cheaper then Mobil 1:eek:
 
#124 ·
bdoug said:
Yeah, I can't normally downshift into 2nd without a double clutch. Once and a while, maybe 20% of the time, it will go into 2nd without double clutching. However, most of the time it feels like the 2nd gear gate isn't even there.
You do realize this is probaly a problem W/ your tranny. and no oil will fix it.:eek:
 
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