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Differential Oil Change

54K views 84 replies 21 participants last post by  Robert.Mauro 
#1 ·
Has anyone done their differential oil changes yet? If so do you have any words of wisdom on how to change the fluids and what gasket/crush washers will need to be replaced.
 
#2 ·
At what mileage/under what conditions is it recommended to replace the differential oil?
My next concern is the 30k service to inspect the CVT and differential oil. Honestly I don’t trust a dealer to do anything more than look at it and call it good, which I really don’t feel like paying for, but I don’t know anything about doing that part of the service myself...
 
#5 ·
According to the service schedule the diff fluid is good for a lifetime unless it sees severe service then it is only good for 15k. Other Subaru’s recommended changing the diffs at 30k. Since I am past the 30k and plan to put lots if miles on my Ascent and gear oil is cheap I thought it would be good to change it out. I am hoping that someone is ahead of me on this one or read the service manual and can tell me how it’s done. Should be fairly straight forward but this is my first Subaru and I want to make sure that there are not any unusual steps to the procedure like on the CVT.
 
#3 ·
There's some good discussion/info on this in the following thread:

 
#4 ·
Recommended is "Inspect every 30,000 miles".

One must make sure that they unscrew the right fill bolt for the front differential (the drain bolt is labeled). The wrong one goes into the CVT.

Check https://parts.subaru.com/ for the latest part numbers, as these do change quite a bit.
 
#7 ·
I changed mine at about 28,000 miles.
 
#10 ·
I changed fluid at 31k miles. I had difficulty finding where to fill. Remove the plug circles in yellow and add fluid until the overflow drains. Pay attention to washers on drain (T70) and overflow because they may drop in drain pan.
 

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#18 ·
The only issue I had was the parts guy at the dealer for some reason assumed the drain and fill plugs front and rear all had the same size gaskets. So I had four new gaskets that only fit the rear drain and fill plugs. The front gaskets were in good shape and I reused them. New gaskets for the front are on order.
 
#24 ·
I know, I’m the other Robert...

I changed mine. That is drained the oil and refilled. I have not heard of flushing a differential before.
I know very little about it myself
 
#25 ·
I had AZP Installs in Kenilworth NJ do it. I've never done it before. So, I've got no idea.
 
#27 ·
Packout - flushing by draining and replacing the fluid and driving some and then draining a second time and refilling a second time is interesting. I do not like power flushing (think coolant and transmission) because that can cause more harm than good. I actually “flushed” my front differential but not on purpose. I was given the wrong gaskets and had to reuse them. I felt guilty about not having new gaskets so a couple weeks later I drained and refilled it again to have new drain plug gaskets.

FYI - the differential oil changes are rather straightforward and easy.
 
#28 ·
I will have to talk with some mechanic buddies of mine. I do not think a flush of any fluid is problematic unless the vehicle has lots of miles on it and the system had never been flushed before. The concern is the flush will loosen up gunk/debri to float around the system.

I am more ignorant than informed on this topic at this point in my research.
 
#33 ·
Rear differential drain plug gasket would be 803918060

You will find it in the drawing in this parts page:


 
#35 ·
Thanks. I haven't done it yet but here is a trick for making rear diff fluid less messy. If you lift the left side of the car when draining you can get a little more fluid out of the drain hole. If you lift the right side of the car when filling you may be able to get the required fill amount in without it coming out the fill hole, which can sort of start a siphon and make a mess and then you don't exactly know how much came out.
 
#38 ·
Finally did this, around 32k miles, I felt that it was definitely time for it . The fluid was dark and a little metallic-y. Very easy with the help of Slippery pete pump. The part numbers you guys supplied were very helpful.
 
#50 ·
I just did my front again and the fluid looked brand new after 29k miles (61k total). I can't remember if it looked this time the first time around. I do reme
Finally did this, around 32k miles, I felt that it was definitely time for it . The fluid was dark and a little metallic-y. Very easy with the help of Slippery pete pump. The part numbers you guys supplied were very helpful.
So I can't remember if I was talking about the front, rear or both fluids here. But I just did the front at 61k miles and the fluid looks brand new (fluid age is 29k miles).

I'm still trying to figure out how to get the corroded rear filler plug off...
 
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