Subaru MT trans fluid

Ausfahrt

Ausfahrt

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I changed the transaxle and rearend fluid in my MT '14 Crosstrek at 50,000 and 100,000 miles. The throwout bearing went out at 130,000 miles and I had a local independent shop do the clutch.

The owners manual specs GL-5 fluid and that's what I used but I have experienced notchy shifting ever since the clutch work was done. It is worst when downshifting from 5th. Sometimes I need to double clutch to get it to go into the lower gear.

I suspect that my local shop just threw in whatever 90wt gear oil that they had laying around and that may be causing my issue. I'm approaching 150,000 miles and I will be changing out the gear oils and then I hope to ascertain if that is what happened.

Thoughts and opinions are welcome and encouraged.
 
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absolutely. Most GL-5 have friction modifiers that are somewhere between horrible and terrible in a manual transmission.

You may want to change it twice.. put something cheap in.. run it for a 1000 miles to get the residue of the old fluid out.. then change it again with your preferred fluid.
such as motul gear 300, redline 75w90NS etc.

I would normally suggest supertech 75w90 as the "cheap clean out" gear oil but it may have been reformulated since I used it for that purpose.
 
MTFs distinguish themselves at large by having the correct friction modification for synchronizers. There are many MTFs that meet GL-4, and extremely few that meet GL-5. MT Subies spec GL-5 because it shares its sump with a hypoid front differential, which needs that level of protection.

Motul Gear 300 & HPL Differential Life 75W90 VOA comparison!

So, as everyone knows from my past posts, I am a big fan of Motul's Gear 300 especially in Subaru differentials. It's the only gear lube I've ever personally used in my 6 Subarus, and it's what I use for all friends and family as well. Its claimed specs are very good; a full synthetic...
bobistheoilguy.com
 
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Ausfahrt said:
I changed the transaxle and rearend fluid in my MT '14 Crosstrek at 50,000 and 100,000 miles. The throwout bearing went out at 130,000 miles and I had a local independent shop do the clutch.

The owners manual specs GL-5 fluid and that's what I used but I have experienced notchy shifting ever since the clutch work was done. It is worst when downshifting from 5th. Sometimes I need to double clutch to get it to go into the lower gear.

I suspect that my local shop just threw in whatever 90wt gear oil that they had laying around and that may be causing my issue. I'm approaching 150,000 miles and I will be changing out the gear oils and then I hope to ascertain if that is what happened.

Thoughts and opinions are welcome and encouraged.
Click to expand...
Usually GL-5 gear oil is not optimum for synchromeshed transmission. But there may be something in the Subaru Extra MT 75w80 gear oil that makes it suitable for their transmissions.

1688748102957.jpg


See Note 4 of the owner's manual excerpt below
1688748020141.jpg
 
You can't go wrong with the Subaru Extra MT 75W-80, but I think they only sell it in 5-gallon pails. The only other GL-5 75W-80 I've found is Motul Motylgear. They also have a 75W-85. A 75W-90 GL-5 will work fine, but fuel economy might suffer slightly. I'd drain out that mystery gear oil ASAP.
 
I used valvoline 75w90 in my 2018 6MT and it always shifted great.

There's a lot of differential action going on there. Shear city! I'd definitely run a GL5 in that application and not a traditional MT lube.
 
twX said:
You can't go wrong with the Subaru Extra MT 75W-80, but I think they only sell it in 5-gallon pails. The only other GL-5 75W-80 I've found is Motul Motylgear. They also have a 75W-85. A 75W-90 GL-5 will work fine, but fuel economy might suffer slightly. I'd drain out that mystery gear oil ASAP.
Click to expand...
I never caught the fact that Extra MT is 75w-80, not 90. Motylgear is now in my scope, too!
www.subaruforester.org

('14-'18) - 2015 - Where to get Subaru Extra...

www.subaruforester.org www.subaruforester.org
 
you have to use a gl-5 unless you want your front differential to self destruct.. they are a combined package.
you need gl-5 for the hypoid gearing.

Some people posting good "general" advice in here but its wrong for this subaru application.

Some of the known lubes that are good for this are redline 75w90ns the subaru extra MT which is thinner but you have to buy in 5gal bucket.. and motul gear 300.

Brian553 said:
I never caught the fact that Extra MT is 75w-80, not 90. Motylgear is now in my scope, too!
www.subaruforester.org

('14-'18) - 2015 - Where to get Subaru Extra...

www.subaruforester.org www.subaruforester.org
Click to expand...

Hey I'm in that thread too from 2016 :)

That motul product wasnt available in 2016?.. but it definitely works..

MOTUL MOTYLGEAR 75W-80 - Motul

MOTUL MOTYLGEAR 75W-80 - Motul
www.motul.com
GL-5 and marketed for transmission use.
 
Follow up:

I changed the front transaxle gear oil and the the notchiness that I had been experiencing quickly disappeared. It confirmed my suspicion that regular 90wt gear oil was used by my local shop and I'm surprised at how it changed the shifting immediately and that a GL5 oil made that much difference.

This is what I put in:
1691484209481.png
 
Motul Gear 300 is the only gear oil that should go in a Subaru manual transmission/front diff combo

Subaru's manual transmissions are combined with a hypoid front diff, so they require special gear oil that promotes good shifting *and* hypoid protection, and Motul Gear 300 is the only one that fits the bill.

Automatic transmissions (CVT and non-CVT) are not combined with the front diff, and they have a separate transmission and differnetial. The automatic transmissions, and their front diffs, are not as picky with fluid. The automatic's front diff can use any 75w90, and the appropriate transmission fluid.

The rear differnetials are not picky at all. Any 75w90 is perfectly fine for the rear.

The BRZ may be an exception since it has no front diff.
 
Redline makes some great drivetrain oils! I recommend Amsoil Severe Gear 75w-90 next time. One of the best gear oil lines in the industry.
 
Ausfahrt said:
Follow up:

I changed the front transaxle gear oil and the the notchiness that I had been experiencing quickly disappeared. It confirmed my suspicion that regular 90wt gear oil was used by my local shop and I'm surprised at how it changed the shifting immediately and that a GL5 oil made that much difference.

This is what I put in:
View attachment 171495
Click to expand...
That’s not “really” the right Redline fluid for Subaru manuals… this is where you’d want the 75w90NS. Hope it works out for you.
 
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