Subaru Maintenance

[slacktide_bitog]

Motul Gear 300 is the best thing to use in a Subaru manual transmission/front diff combo

The rear diff can use any 75w90, so just get the cheapest synthetic on sale

 

[AJB0009]

There should only be 2?
FRONT DIFF+MT and REAR DIFF.

For the rear any 75w90 gl-5 gear oil.

For the shared sump with MT you need a gl-5 gear oil that works well with the synchros in the transmission.

Redline 75w90NS, Motul gear 300 etc.. avoid anything that says it has limited slip additive.

I have wondered about this. I was going to do my son's rear diff on his 21 Crosstrek. They are all "open" diffs, correct? So, would a person NOT want something that has limited slip additive included? Doesn't that add some sort of "grit" to the oil?

 

[GSCJR]

My Legacy has plain old conventional 80w-90 GL-5 in the diffs.

 

[BISCUT]

I'm confused now is your 17 a Stick shift? if not it uses CVT fluid and is separate from the front diff.
So I think you are talking about something diff-erent than I was.

the 98 the OP has ... has a combined front diff/MT that shares gear oil.

Rand, the 17 is a 3.6 and a CVT. The CVT shares a bath with the AWD unit. Power is biased to the front and the front diff oil shows the difference when compared to the rear diff. That's my understanding of the 17 3.6 arrangement.

 

[Rand]

Rand, the 17 is a 3.6 and a CVT. The CVT shares a bath with the AWD unit. Power is biased to the front and the front diff oil shows the difference when compared to the rear diff. That's my understanding of the 17 3.6 arrangement.

Yes the multi plate clutch is bathed in cvt fluid your front diff is separate and gear oil.

On MT equipped AWD Subaru the mt shares gear oil with the front diff

 

[BISCUT]

Yes the multi plate clutch is bathed in cvt fluid your front diff is separate and gear oil.

On MT equipped AWD Subaru the mt shares gear oil with the front diff

Phew! We're on the same page now!

 

[Rand]

I have wondered about this. I was going to do my son's rear diff on his 21 Crosstrek. They are all "open" diffs, correct? So, would a person NOT want something that has limited slip additive included? Doesn't that add some sort of "grit" to the oil?

it's fine there's an extra additive so that it has the right coefficient of friction for clutch/friction based limited slips. it is not detrimental in an open diff.

 

[AJB0009]

Yes the multi plate clutch is bathed in cvt fluid your front diff is separate and gear oil.

On MT equipped AWD Subaru the mt shares gear oil with the front diff

Wait... (Sorry, I don't mean to hijack this post)
On my son's 21 Crosstrek, is the CVT and front diff separate?

 

[IndyIan]

Wait... (Sorry, I don't mean to hijack this post)
On my son's 21 Crosstrek, is the CVT and front diff separate?

They are, which is good so they take optimized fluids for each.

 

[Rand]

They are, which is good so they take optimized fluids for each.

Automatics and cvts were always separate only on the manual transmission equipped all-wheel drive Subarus where they a combined unit with the diff.

 

[Pablo]

All I know is the Subie 5 speed MT ca 2014 was a pretty junky transmission combined with a shear o matic transaxle led to people trying all sorts of cocktails. But they all sheared.

 

[D60]

I have wondered about this. I was going to do my son's rear diff on his 21 Crosstrek. They are all "open" diffs, correct? So, would a person NOT want something that has limited slip additive included? Doesn't that add some sort of "grit" to the oil?

The FM doesn't hurt a thing even if not needed -- in diffs. I'm not speaking of manual transmissions, which can be picky.

Very few manufacturers have used a clutch or mechanical type limited slip in the past ~15 years. Most are computer based traction control.

 

[SubieRubyRoo]

A late 90's Subaru with intact rear wheelwells? I don't think I've seen that since those came out new around here!

Must be a California car

 

[D60]

I also service a '98 Legacy with the 2.2 and an automatic. That poor thing is hurting (high miles + neglect) but no rust here in Southern CO

 

[slacktide_bitog]

I also service a '98 Legacy with the 2.2 and an automatic. That poor thing is hurting (high miles + neglect) but no rust here in Southern CO

I wish the Forester had that engine instead of the awful EJ25D

 

[SubieRubyRoo]

I wish the Forester had that engine instead of the awful EJ25D

The only thing awful about the 25D was the single-layer steel head gaskets from the factory, along with ground cables that frayed worse than a teenage girl’s split ends

 

[slacktide_bitog]

The only thing awful about the 25D was the single-layer steel head gaskets from the factory, along with ground cables that frayed worse than a teenage girl’s split ends

and it was press fit against the frame

Thankfully, head gasket sealers have gotten good. It's the reason that older Subarus are finally worth buying