Front/Rear Differential Fluid Change

[Grnlantern1]

I like Motul.. When it's time I'm swap it out..

 

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[spect2k]

Just a suggestion... Next time take pics of the plugs you did drain and post them up!!

As you saw from the beginning, I was figuring it out. I ended up buying the service manual. The pix I took were when I was looking for some support. I decided to explain the process to everyone after I did it so others could avoid the same issue. This was never supposed to be a diy, but a request for help. Because I didn't take pictures of everything, that is why I explained in detail after. Hope it's helpful as is...

[Too40gawlf]

As you saw from the beginning, I was figuring it out. I ended up buying the service manual. The pix I took were when I was looking for some support. I decided to explain the process to everyone after I did it so others could avoid the same issue. This was never supposed to be a diy, but a request for help. Because I didn't take pictures of everything, that is why I explained in detail after. Hope it's helpful as is...

 

Where did you buy the FSM? Was it on electrons or hardcopy? And how much was it?

[spect2k]

http://legacygt.com/forums/showthread.php?t=244422

[apexi]

When Subaru says to inspect, chances are they mean just the fluid level and not condition.

 

If you have not replaced your diff fluids yet, I don't think it's a bad idea to at least do the rear differential. I use to have Subaru do the rear diff fluid on my 4th gen, and the price wasn't too bad at between $40-60 depending on the dealer. I can't imagine 6th gens being much different price wise, but you could always call for a quote.

 

The thing with brake fluid is that it's highly hygroscopic, and attracts any moisture it can get. That's probably why Subaru recommends changing the fluid every 2 years, to get any moisture out of the system. So in my opinion do you have to change your brake fluid ever 2 years? No. Should you? Yes. Brake fluid I don't replace myself, I pay subaru to do that. I think they charge around $140-$160 to replace the brake fluid on my 4th gen. So I guess to me, paying $140-$160 to keep my braking system healthy and ensure longevity isn't too bad.

[BEADS]

The manual says to use Subaru MT fluid. GL-5 is a second choice.

 

I wonder if friction modifiers should be avoided since its a limited slip differential.

 

I decided to do my myself since my dealer wants to charge me $190 to do both differentials!

[hkshooter]

Some of these threads are interesting and it's interesting to see the views of people concerning maintenance items.

I'm aware that technology changes and so does the service required but for simple items I have to wonder how much of it is simply an excuse to give the servicing dealer more money. How does SIA determine when the diff fluid needs changed? Or a big one for me, brake fluid?

As has been said there is no clear recommendation of when the diff oils need changed, just checked. I've owned passenger cars with well over 200k on the clock that have never had the diff oil even checked since new, let alone changed, and all worked well when the car finally met the crusher.

Brake fluid changes are particularly puzzling to me. Yes, brake fluid sucks up moisture like a sponge which can rust parts. BUT, is the system vented? No, of course not, other wise it would puke fluid every time the brakes are pressed. So by necessity the system is completely closed. So where does the water come from? No need to take the cap off the master to check level. This is another one of those long legged items I for the life of me cannot justify the cost of, brake fluid replacement. Call me old, I've had many cars over the years, none of them ever had the brake fluid changed. Topped off and bled, depending on the repair? Yes. Have I ever had brakes fail? No.

The first time someone told me their dealer wanted to change the brake fluid I nearly fell over laughing. This was for a Toyota tundra.

They also wanted to change the belts and replace all the brake linings. The truck had 9k on it. And they expect that a little old lady (literally, my mother) knows squat and will pay up simply because the dealer said so.

I realize this is my own opinion and it's worth exactly what you paid for it but I see many of these "services" as money making BS services that are dreamed up simply as money makers for the service departments. The "gotcha" is they can be demanded they be performed to keep one's warranty in tact. Sneaky.

I'll have all the recommended stuff done to my own car until the warranty expires, just in case. But after that it'll get all the service I normally do based on my own experience (26 years in service and repair in dealerships) and common sense. Trust me or not, service departments are always looking to sell a service (duh) and up sell if possible. I've went round and round with my own service dept's in arguments about ethics and morals when it comes to performing a service that's absolutely not needed but is a money maker for the shop. On one hand, are we performing that service? Absolutely, yes. So the charge is legitimate. BUT is that service really needed? Sometimes NO and when I question the service manager is when I get the arguments.

 

People may use whatever advice they want to determine what service they perform, be it word of mouth, dealership, service dept recommendations, or rare unicorn sightings. Some folks I imagine are simply bored and their car is their hobby. Fair enough.

I simply feel like some of this stuff is a waste of time and money especially considering some are worried about the longevity of a fluid in a vehicle they will most likely trade off in a couple of years.

To each their own, do what makes us happy. Me? I'll do what makes sense to me much like everyone else does and that certainly isn't going to be brake fluid changes every two years or diff oil that doesn't need to be changed at all.

Edited February 28, 2016 by hkshooter

[ammcinnis]

The manual says to use Subaru MT fluid. GL-5 is a second choice.

 

I wonder if friction modifiers should be avoided since its a limited slip differential.

 

I decided to do my myself since my dealer wants to charge me $190 to do both differentials!

 

So much misinformation in such a short post.

 

1) From the 2015 Legacy/Outback Factory Service Manual:

Front differential (H4: page CVT(TR580)-4) - Subaru Gear Oil Extra MT or equivalent

 

Front differential (H6: page CVT(TR690)-4) - Subaru Gear Oil extra MT

CAUTION:

If an alternative transmission oil is used, you may not have expected functionality and performance.

Alternative fluid: GL-5 75W-90

Rear differential (page DI-2) - GL-5 75W-90

2) The 2015/2016 Legacys and Outbacks have open differentials (not limited slip), both front and rear. Aftermarket friction modifiers should be avoided anyway.

 

3) $190 might be a bargain in the long run to have it done right.

Edited February 28, 2016 by ammcinnis

[brohloff]

Agree w #33 post above re changing brake fluid every couple years. Is it good to do? Sure won't hurt but not really necessary.

IMHO is sorta like changing engine oil way early (i.e. at 2000 miles like it used to be). Or like doing transmission fluid change early......

Is it good to do? Yes...get better oil/fluid in car sooner..... Sure won't hurt but not really necessary.

I might agree that changing the brake fluid at 100-120k miles (esp if it's been leaking and fluid has gone down and the air it's sucked in to replace the lost fluid is humid) is good....But earlier than that, again IMHO, is overkill.

Not to belabor the brake fluid point BUT if one wanted to do some PM on the brake system that IS useful every year or two would be to lube the caliper pins and moving parts so that the pads continue to move freely. Hung up pads are hard on pads and rotors. Unlike the sealed brake fluid system these things hang out there in all that salt, water and grim and can use all the help they can get to stay free......

Do I do this?...NO...Should I? Yes.....Too lazy/much work I guess....

Sorry if too much TMI...

[apexi]

I completely understand what hkshooter and broholff are saying. I guess for me, I don't mind paying $140 every couple years to make sure my braking system says as healthy as possible.

 

I think it's good to change the diff fluids at least one time, to clean off the magnetic drain plugs and get rid of any crud that might be floating around in the fluid. After that I don't think it's the end of the world if you don't replace it, as long as the level stays good. My reason for changing it is that I can do it myself pretty cheap, and I worry that the transmission/rear diff fluid shears the fluid down and lowers the viscosity over time.

 

On my 4th gen, the caliper slide pins are actually sealed pretty good, I have never had a problem with mine losing their lubrication even after 150k+. You can kind of see what I mean in the image below from a 4th gen, and it looks like your 6th gen's should be the same way. The caliper slide pin has the rubber boot around it , and the bolt in the back screws into the slide pin.

http://i.ytimg.com/vi/VTw2vTZwkYs/maxresdefault.jpg

[hkshooter]

Due to the efforts of the OP I'm changing my thoughts a bit concerning the brake pins and hardware. I now believe those parts need attention periodically if I haven't already worked on them myself. Once I've been through the brakes myself I'm confident they will not have problems while there is still life left in the pads, due to past experience.

But as for the brake fluid itself I like apexi's approach. I may change or have it changed out at some point just to help satisfy the warranty but beyond that it won't get changed unless there's a leak or other indication that there's a need.

The diff fluids will get checked for level and the CVT will be changed out at some point, maybe three or more times if the car sees 200k in my possession.

[spect2k]

So much misinformation in such a short post.

 

1) From the 2015 Legacy/Outback Factory Service Manual:

Front differential (H4: page CVT(TR580)-4) - Subaru Gear Oil Extra MT or equivalent

 

Front differential (H6: page CVT(TR690)-4) - Subaru Gear Oil extra MT

CAUTION:

If an alternative transmission oil is used, you may not have expected functionality and performance.

Alternative fluid: GL-5 75W-90

Rear differential (page DI-2) - GL-5 75W-90

2) The 2015/2016 Legacys and Outbacks have open differentials (not limited slip), both front and rear. Aftermarket friction modifiers should be avoided anyway.

 

3) $190 might be a bargain in the long run to have it done right.

 

Gospel.

 

Experience tells me that brake fluid lasts about 4 years or so in my climate (CT). This is determined by moisture content using a brake fluid tester. I've seen as little as 3 years, and as much as 6 years. Different fluids behave differently.

 

Diff fluids are a good thing to change around 30k IMO. Magnets are pretty filled at that point from my experience with Subarus breaking in. After the first change using a high quality fluid, I'd then go another 50-75k on the new diff fluids. Best you can do to "check" the fluids is to take out the fill plug and check the level. This doesn't tell much about the condition of the oil. Also, fluid will likely come out of the fill plug as well. If you are already down there "checking" the fluid level, it is only one other bolt and some fluid to change it out. Some Toyotas are having rear diff growling issues with people that have never changed out fluid. I've been doing a bunch of them and those that have been serviced aren't having any issues. Just my experiences.

[mr2guru]

Changed mine out over the weekend at 25k... fairly nasty fluid and magnets were gunked up with no discernable particles of size. Replaced with Mobil1 75w-90 front and rear.

 

The front under tray was the biggest pain.

[andrew_l_s]

Attempted my diff fluid change this weekend. The front fill plug stripped on my so I ended up accomplishing nothing.

 

I can't find a replacement plug on parts.subaru.com if someone knows the p/n or can find one please let me know. I'm hoping to purchase one and let a local shop handle it vs. overpaying the dealership.

 

Also, the rear diff isn't 8mm. I tried using the 8mm I purchase for the front and it's way too small, my guess is it's 10mm but I'll check for sure before buying the driver.

[Anthonyg]

Fluid should be changed in severe conditions at. Every 15k if towing to normanl would be just driving it should be done every 30k

[ammcinnis]

Fluid should be changed in severe conditions at. Every 15k if towing to normanl would be just driving it should be done every 30k

 

You can change fluids in your Legacy as often as you want, but that is not Subaru's recommendation.

[Opie]

Great article on brake fluid replacement: https://www.cars.com/articles/how-often-do-i-need-to-change-my-brake-fluid-1420680336417/

[STI_.]

I had the dealer do new brake fluid. Roughly $130. Not sorry I did. I'll likely keep this car longer than any I've kept in my life. It's almost a game with my wife these days - she says "you will NEVER keep it longer than 3 years. [emoji41]

 

 

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[Matt_75]

Sorry to bump this thread. I have a 2016 legacy with ~29k on it. I decided to change my front/rear diff. I read through all these pages and had no problems doing the drain/fill on both the front/rear. My concern is I filled both front/rear fluids until they began to overflow from the fill plug. And yes, I used the fill plug on the passenger side above/next to the drive axle. The front diff ended up taking 2.5 quarts of fluid before it started dripping out of the fill plug. And yes, it was drained from the T70 torx drain plug in front of the CVT pan.

 

My question is, should I drain it and put 1.5 quarts in even if it doesn't start dripping from the fill plug or should I just leave it since I did what the OP did and let it drip from the fill plug?

 

Any insight or help would be much appreciated.

[ammcinnis]

Any insight or help would be much appreciated.

 

You filled the front differential incorrectly. It is now overfilled.

 

You don't fill until oil flows out of the fill hole. There is a separate "overflow drain plug." To quote from the Factory Service Manual, page CVT(TR580)-46:

Fill in the differential gear oil through the filler plug hole up to where the oil flows out of the overflow drain

plug.

If you're going to be doing maintenance stuff like this yourself, which I highly support, you really need to get a copy of the Factory Service Manual. Edited January 6, 2018 by ammcinnis

[Matt_75]

You filled the front differential incorrectly. It is now overfilled.

 

You don't fill until oil flows out of the fill hole. There is a separate "overflow drain plug." To quote from the Factory Service Manual, page CVT(TR580)-46:

If you're going to be doing maintenance stuff like this yourself, which I highly support, you really need to get a copy of the Factory Service Manual.

 

Great. Thanks for the response. I found the "check" overflow plug for the diff next to the diff drain plug. I plan on opening and letting the fluid drain tomorrow. I drove it earlier about 8 miles. Do you think I did any damage to the front diff?

Edited January 6, 2018 by Matt_75

[Too40gawlf]

Matt,

 

You didn’t do any damage. As a rule of thumb, I’ve always filled a diff to the point where it starts to just trickle out the fill hole. Apparently the Subaru method is different.

 

Anyway, just do as you mentioned with the check plug and let the excess drain out.

 

If you like, PM me and I will get you an FSM for our cars.

 

Good on you for actually turning a wrench and not making a post about LED lights and spoilers.

[YeuEmMaiMai]

I changed out my diff fluid out at 35K it looked good as new. I wanted the dealer to do a drain and fill on CVT and they said no...

[Pilot1226]

I had them tell me the same for my CVT. I was concerned and skeptical about "lifetime" change interval.

 

Basically, I heard back that there's a chance to disrupt any "particulates" in the bottom of the pan itself with a drain and fill, and even if you do the D&F, you're only going to get around 6 out of the ~11-12 quarts out of the transmission, so at best you're only looking at 50% new fluid...

 

Transmission Fluid is a great "cleaner" - so it's possible that you could dislodge something from the pan that was otherwise "out of the way" and have it gum up the valve body, I guess, is their line of thinking.

[ehsnils]

For the CVT I'd probably look into a fluid change at 40k miles or something.

 

It's more a question of aging of the oil than anything else.

 

Unfortunately the fluid is quite expensive so it's not something you want to do too often.