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Discussion Starter #21
I'll be doing both diff fluid changes myself as well in the near future. How much replacement fluid is needed for each diff? I normally use Mobile 1 or Royal Purple - does that work well for Subarus (this is my first Subaru).
The manual says to use 75w90 meeting the GL-5 standard. I think they both meet it but check the bottle to be sure.
 

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Discussion Starter #23
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.
 

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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
 

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I had AZP Installs in Kenilworth NJ do it. I've never done it before. So, I've got no idea.
 

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Discussion Starter #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.
 

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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.
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.
 

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Discussion Starter #29
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.
The loosing up of gunk on older cars is one concern of flushing. Another is the harsh chemicals they use. One more is the high velocities (Reynolds number if your an engineer). Transmissions have small passages and cooling systems can have choke points where the localized velocity of the flushing fluid would high enough to cause erosion. All said there are too many risks for the small rewards when it comes to power flushing either a trans or cooling system. Your opinion may vary....
 

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The loosing up of gunk on older cars is one concern of flushing. Another is the harsh chemicals they use. One more is the high velocities (Reynolds number if your an engineer). Transmissions have small passages and cooling systems can have choke points where the localized velocity of the flushing fluid would high enough to cause erosion. All said there are too many risks for the small rewards when it comes to power flushing either a trans or cooling system. Your opinion may vary....
It may vary if I actually knew much about it at all, which I do not. I prefer well informed opinions of which I have none on this subject. Thanks for the detail.
 

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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.
I don't suppose you have the gasket PN's for front/rear?
 

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Just for the front because I orders over the internet and found the email
803916100 over flow plug
803926090 drain plug
Rear differential drain plug gasket would be 803918060

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


 

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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.
 

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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.
 
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