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Front/Rear Differential Fluid Change


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Going to change out the fluids on both front/rear diffs.

 

Anybody done it yet?

Same as 5th gen CVT model?

 

I could use torque specs and any other specifics if anyone has a copy of the service manual.

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Ehh, like 15k. Wanna get the old stuff out that went through break-in and don't wanna deal with it over the winter. I'd normally go up to 30k for the 1st change (up to 60k with a really good synthetic after that).

 

Job costs next to nothing to do and is really easy, so little downside. Worst case, a waste of money. Best case, changing fluids on a car is almost always a good thing.

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According to the maintenance schedule on here:

http://www.cars101.com/subaru/maintenance-2015.html#notes

 

You only need to "inspect" the differential fluids every 30 month or 30k

 

I guess that means, after inspecting it, if there is no issues with it, you can just leave it and forget it. They don't call for scheduled replacement.

 

I know changing fluids is always good for the car, but wouldn't it be waste of money and time to replace something so early thats not even required to be replaced?

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Could use some help here. Not sure what parts are for CVT and what is for front diff. Definitely different than the 4th gen from what I remember.

 

There seems to be a clear CVT drain plug underneath and then a bunch of 8mm hex. I'm assuming we are looking at a fill/drain for each, but not sure. Not sure if there is a fill, drain, and overflow for front diff. Help would be greatly appreciated!

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Edited by spect2k
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Now that I've done the job, let me give some pointers and specs for everyone doing this job in the future.

 

First, since I was probably the first person to do this work, I ended up getting a subscription for the 2015 factory service manual. More info on THIS THREAD.

 

The biggest warning I will give is to be HYPER aware of what you open before you open it. There are quite a few 8mm hex fasteners down there. Some are for the front differential and others are for the CVT! Again, a warning, do NOT open your CVT. If you don't know what you're doing or you're not 1000% sure, do NOT continue. Do the rear diff yourself and have the dealer do the front.

 

Front Differential:

 

Fill plug access is above the passenger side axle. In the picture in my previous post, you can see it with the axle in the picture. To access it, you have to take off the front passenger wheel. Maybe you could get there another way, but not that I saw.

 

Drain plug for the front differential may be confused for the FILL plug for the CVT! (see warning above). In the 1st and 2nd picture in my previous post, you can see that the CVT fill plug is very convenient (on the side facing the drivers side of the car)! These are NOT for the front differential. The front diff drain plug is in front of the CVT pan, not behind it (in line with the axle). It also uses a T70 torx bit. That should be clue enough. I don't have a shot of it, but you need to take off a cover to access it.

 

The FSM has generic images of the area that aren't so great, so I hope mine are helpful.

 

Torque Specs: 36.9 lb/ft torque on 8mm hex, 51.6 lb/ft on T70 drain

Quantity: ~1 quart (until overflow is achieved)

Fluid Type: 75w90 (I used Amsoil)

 

Rear Differential:

 

Rear differential is much easier. I don't have any photos for it. If you wanna see it, just tilt your head sideways under the back of the car like you're 16 and looking up a hottie's dress. Two 8mm hex fasteners that need to come out. Always do the fill first (in case you can't get it out). I had the car up in the air for this. It may be doable on the ground, but it'd be tough. Plus, the drain plug was on tight!!

 

Torque Specs: 36.9 lb/ft torque (fill & drain)

Quantity: ~1 quart (until overflow is achieved)

Fluid Type: 75w90 (I used Amsoil)

 

 

Both front and rear fluids looked pretty good at 15k. The rear diff drain plug magnet was LOADED and all gunked up. Glad I changed it out, and while the magnet was nasty, I'd recommend 30k for the first change just based on the fluid. The magnet did it's job though. Also, there are washers on there that should be replaced, although I didn't.

 

Hope this helps the next person!

Edited by spect2k
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Totally works too. Peace of mind. My dealer wanted ~$150 for the job. I had the fluid laying around from other jobs I've been doing and the whole thing took me about 1 hour once I had the service manual.

 

Not to force it, but I'd totally encourage anyone that hasn't done this kind of work before to try the rear diff. It it really easy to do and builds some confidence for that sort of work.

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Can quiet things down - did you notice anything? Our 05 Impreza had shuddering at 50k. Changed tranny and rear diff, that took care of it. I did the fronts after I got it back. Our 06 Forester was OK but I changed at 50k and it got smoother and quieted down. I used Swepco Smurf Blood popular with Subie performance shops.
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Nah, didn't notice any changes. But the big difference is that this is a 2015 with 15k miles on it - very different from the other two you referenced. Also, I didn't do the transmission fluid.

 

I didn't do this work to solve any problems. I had the fluid laying around (cost me nothing other than an hour) and I'm not going to be able to do this kind of work for the foreseeable future, so I needed to get it taken care of now. I think of this as preventative maintenance. By 50k, you could be doing the work to solve a problem as you suggested. I think 30k is the right interval from what I've seen.

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Does the 2 years service program covers this ?

 

You will have to look it up in your docs. Most of the country doesn't get the 2 yr service program.

 

If I had to guess, assuming the 2 year plan is for 2 years/24k miles, then no, since this service is typically part of the 30k service.

Edited by dsn112
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Is there some documented evidence that this needs to be

done in lieu of the service intervals in the maintenance manual?

I just can't see spending the time or money on something that is

not needed. To me this is like changing oil at 3K miles instead of the

recommended 6K. Unless you have a proven need, why ??

Edited by balbrec2
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Is there some documented evidence that this needs to be

done in lieu of the service intervals in the maintenance manual?

I just can't see spending the time or money on something that is

not needed. To me this is like changing oil at 3K miles instead of the

recommended 6K. Unless you have a proven need, why ??

There is no service interval in the manual other than to inspect. It also says to replace at 15k under sever service (towing and such). There is plenty of evidence to say this job should be done, but the interval is much more debatable.

 

To use your analogy of oil changes, there are some that do their first oil change at 1k miles and then every 3-6k after that. There are some that do every 6k and you even have extremists who follow Amsoil's 25k! My changing it as early as I did equated to that first 1k oil change in my mind. Perhaps the 30k equates to the standard 3k oil change and 50k to the 6k oil change. However u want to look at it, you have to do what you're comfortable doing.

 

As I said, my fluid looked good but the magnet was full. I've done first time diff fluid changes at 50k and it was pretty nasty. Subsequent 50k changes with good synthetic typically looks a lot better in my experience.

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spect...we all do what we feel is best and I certainly don't fault you for changing your fluids early. I am one of those guys that does his first oil change at around 2500 miles and then every 5K religiously with synthetic only. I will, most likely, change my diff at 30K unless I feel there's a good reason to go early.
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spect...we all do what we feel is best and I certainly don't fault you for changing your fluids early. I am one of those guys that does his first oil change at around 2500 miles and then every 5K religiously with synthetic only. I will, most likely, change my diff at 30K unless I feel there's a good reason to go early.

👍 thought I was saying the same.

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  • 1 month later...
Thank you to Spect2K for the detailed posting with pics. I was about to begin drain and fill of the diffs last weekend, after a regular oil change, but decided against until I could find the fill plug for the front. Glad I waited. And I did get new washers. I am going to use Valvoline synthetic 75w90 BTW.
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Good job OP - I though about doing this with my 1K break in oil change, but figured, I would just let it go till the 30K interval. Ive never done preventative changes on differentials before and havent seen any issues. Although, I cant fault you for getting a jump on it.

 

Maybe I missed it, but what fluid did you use? Im a fan of Mobil1 75w-90 which Ive used for other vehicles, but was wondering what you went with.

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That's a great fluid. I used Amsoil as I had it laying around. I also think it is top of the line fluid.

 

Sometimes you've gotta do things when you've got the chance. I would've waited to 30k also, but life gets in the way!

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