Subaru LEgacy GT 5MT trans fluid?

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Been doing some research on the best fluid for my wifes 08 Legacy with the 5MT, its very "notchy" IMO and I Hear thats a common complaint with these boxes unless you put the right fluid in them. I changed it last year when we bought it and just used Valvoline &%w90 GL-5 like it called for but I'm not liking it.

Many say to use Redline 75w90NS, some say royal purple syncromax, some say the Pennzoil synchromesh etc... what will give me smooth shifting and proper protection for this already weak gearbox?

Any personal experience?
 
Notchy is right. Here's a list of what I've used in Subaru 5-speed gearboxes over the years, from best to worst.

Subaru Extra S (discontinued)
Mobil Delvac 1
Red Line NS
Motul Gear 300
Valvoline Conventional
Subaru HPGO (replaced Extra S)
Amsoil Severe Gear (this was especially grindy)
... others ...

If you can find the Delvac, that was my favorite out of what's still produced. A local Mobil distributor may be able to help.
 
Friend of mine is a big subaru guy. He says the Scoob people make a concoction out of different brands in different quantities for the best feel. You'd have to look through the subaru forums. Subaru people can be really weird.
 
Since the discontinuation of Extra-S, the only fluid I'd use is the Subaru High Performance Gear Oil.
 
Subaru's own Extra-S was fantastic stuff but is now apparently scarce if not gone.

Fred Beans in Doylestown PA used to break it down into quarts and sell it on Amazon which is where I got mine. It may be worth a call to their parts department: https://www.fredbeans.com/

Beyond that, any cocktail recipe you find online is just a band-aid for worn synchros.
 
As someone who owned one of those subaru MT's (and multiple other subaru MT)

I've heard good things about the Delvac gear oil.

I personally feel the motul gear 300 was the best I used.. followed by the redline 75w90NS, then supertech 75w90 blend.

I would stay away from smurfblood and any other exotic mixes.
Make sure you are using a GL-5 rated gear oil.. many MT specific gear oils are only api GL-4.
 
Originally Posted By: Bottom_Feeder
Subaru's own Extra-S was fantastic stuff but is now apparently scarce if not gone.

Fred Beans in Doylestown PA used to break it down into quarts and sell it on Amazon which is where I got mine. It may be worth a call to their parts department: https://www.fredbeans.com/

Beyond that, any cocktail recipe you find online is just a band-aid for worn synchros.

The Extra-S is long gone. Some folks have been selling the new HPGO as Extra-S. It's not, and it's awful in the 5-speed gearboxes.
 
GL-5 MT is for HD truck NON syncromesh trans. It will kill blocker spinup on a PC tranny with phos bronze rings.

So have good synchro action and kill the differential gearset with GL-4.
 
I'd stick with Subaru High Performance Gear Oil, or Motul Gear 300. Subaru does call for a GL-5 in it's manual trans, but I've had better performance (less notchiness) with these two.
Don't use a cocktail.
 
Originally Posted By: racin4ds
Been doing some research on the best fluid for my wifes 08 Legacy with the 5MT, its very "notchy" IMO and I Hear thats a common complaint with these boxes unless you put the right fluid in them. I changed it last year when we bought it and just used Valvoline &%w90 GL-5 like it called for but I'm not liking it.

Many say to use Redline 75w90NS, some say royal purple syncromax, some say the Pennzoil synchromesh etc... what will give me smooth shifting and proper protection for this already weak gearbox?

Any personal experience?


I've been using Amsoil 75W-110 (not 75W-90) in my 2014 WRX for 30K miles and it's still as slick as the day I put it in: Amsoil 75W-110
 
Thanks Guys, yea I'm seeing the same thing... all kinds of concoctions and mixes these subaru guys use... Not too fond of the mixing.

I think I'm just going to go with the Redline NS first, many praise that stuff and its easy to get.
 
Originally Posted By: racin4ds


...Many say to use Redline 75w90NS, some say royal purple syncromax, some say the Pennzoil synchromesh etc... what will give me smooth shifting and proper protection for this already weak gearbox?...

Any personal experience?


I would not use any of the above since they don't have the right viscosity or wear protection, or friction modification, nor do most carry they carry the GL rating your common sump gearbox requires.

I would recommend:

https://www.redlineoil.com/product.aspx?pid=43&pcid=7
 
MotulGear 300 75W-90 seems to work very well in the Subaru 5MT from personal experience. Redline is not a good idea, the Redline 75W-90NS sucks, it'll ruin the synchros in no time and make it VERY hard to shift. The best fluid used to be the old Subaru 'Extra S', which is NLA and even if they tell you they have it - they don't, what they're selling over the counter is a 75W-90 conventional or at ebst syn blend gear oil. Don't bother with that stuff.

And I also agree with Molakule, the Synchromesh's are just the wrong fluid for this application. I've never tried the 'Smurf Blood' in them though. You really think thats an OK fluid for them?
 
Originally Posted By: ARCOgraphite
Nevr hear d a Subaru MT gearbox called weak!

Now a B-W T5 in a ford mustang - there's a piece of , well boat anchor.



The 5 speeds are [censored]. Stronger than a T5, sure. Even a lightly modded WRX can break gears though, and they all wear synchros out in no time if you even remotely try to shift them fast. They just aren't built to withstand any kind of abuse whatsoever. If you can be nice to it ti's whole life, sure.....


The 6 speeds, otoh, are near bulletproof.
 
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