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Change out your rear differential fluid now!

81K views 54 replies 40 participants last post by  DockingPilot 
#1 · (Edited)
After only 23,000 miles I had lots of shavings and a square chunk of metal the size of a BB clustered around the magnet. The dino oil looked trashed too. I know I probably wouldn't have had this much wear and tear if I had switched to Motul 300 synthetic in the beginning. :icon_cry:

So what causes heavy wear in the rear differntial? It's not like I am enaging it manually like the transmission....replaced that with Motul 300 too because it it looked like tea. I'm thinking 20K intervals should be about right for the rear differential but I'm thinking 30K for the transmission. Shifts like a drream now! :biggrin:
 
#36 ·
I changed my rear diff oil last week as you can not check it or know the level or condition.
The level was ok
Mine was a bit dirty
But here was a few metal filings stuck to magnet

I feel better know it was changed, i will properly change it again soon to give it good flush.
Used Castrol 75-90 Syntrax Synthetic
 
#39 ·
I changed my diff oil on my Tacoma at 100,000. Stinky but no metal particles. I think some of you guys may be ocd. Also changed my oil on my olds delta 88 at 50k and it was fine. Maybe:, Subaru really is needed early. 15k on mine and it looked fine. I sucked my front oil on mine and it looked fine. I'm doing mine once a year since I don't beat on it.
I need more reason to do it sooner because it doesn't look bad enough to panic.
A little metal shavings on the plug is normal.
 
#41 ·
rear diff oil change help

hey all-
I have now done the front and rear diff's on my 2010x manual 2 times, once at 15k and now at 30K.
the fronts with the manual are serving double duty as clutch and trans fluid as well as diff fluid, so these were much dirtier that the rear.
***many of you may have already figured this trick out, but when you are adding fluid to rear diff, it can be a real pain if you don't have a pump to combat gravity of the fluid having to rise to get into the filler hole***
I found that if you take out the spare tire from the inside of trunk/hatch and remove the right rubber grommet/drain plug, you can run a line with a funnel attached and dump the .8 qts right in with no need to squeeze the S&*# out of the fluid bottles etc...
Hope this helps.
 
#42 · (Edited)
have a pump to combat gravity of the fluid having to rise to get into the filler hole***
I found that if you take out the spare tire from the inside of trunk/hatch and remove the right rubber grommet/drain plug, you can run a line with a funnel attached and dump the .8 qts right in with no need to squeeze the S&*# out of the fluid bottles etc...
Hope this helps.
Well..good idea. I merely buy two bottles, squeeze in as much of the first bottle as possible. I then do the same with the second bottle. That is more than enough. I then pour the end of one bottle into the other. Takes about 1 minute. Faster than your method but good innovation .:biggrin:
 
#46 ·
I have an 08 X auto, but used to have an 05 X auto that is similar to yours.

Rear diff: About .8 qt. Some runs out the diff fill hole when full so you might use a little more.

Front diff: About 1.2-1.4 quarts. I've never used more than about 1.1-1.2 quarts to refill my front diff to the full mark on dipstick.

So 2 quarts of your favorite 75W-90 gear oil will suffice for both diffs.

The front diff requires a Torx T-70 to open. It also has a washer that is bigger than the oil/trans drain plug crush washers. I've reused mine once or twice without a problem, but you can get one at the dealer for less than $2.

As for ATF, I've done several drain and fills through the years. I prefer to leave the car overnight and drain when cold to get the most fluid out. I measure what comes out and it's usually 3.5-3.8 qts (never more than 4 qts).

I put in the same amount that came out. Temp affects volume of ATF so make sure you let hot ATF cool for an accurate measurement. Otherwise you might overfill if you refill with cold ATF. That's the reason I like to do it cold...old and new ATF are the same temp/volume.

In my 08 I use Subaru ATF HP which is backwards compatible to all years, but I think for 05 and earlier you can use regular Dex III ATF from Subaru or aftermarket. Your owner's manual should tell you for sure.

Good luck.
 
#48 ·
Yea good information. Don't worry about a gasket for the front diff. Again the rear diff is a ***** to losen. Backing up on a ramp gets you leverage. Just inspect the gasket for the auto tranny. Replace if you want. Don't overtighten the rear diff. You don't need sealant.
 
#50 ·
I have M1 and Amsoil SVG on hand. Going with SVG in rear diff.

There were a few recent UOA's on BITOG comparing Synpower/SVG and I was surprised at how much lower the Fe wear was with the Amsoil. Mobil just updated their PDS for their 75w90. That too is an excellent rear diff option (not MT). It came in 2nd place in Amsoil's white paper.

Extra-S is my favorite in the MT.
 
#51 ·
Changed my rear diff oil this past weekend and did a pretty amateur move. I undid the drain plug, drained the oil, cleaned the plug, installed the plug with no issues. Went to undo the fill plug and couldn't get it off. Soaked it down with anti seize, hammered on it, soaked some more, heated it up with a blow torch. Tried everything to get it off, but it would not budge. Got on my bike and pedaled down to the hardware store to buy a breaker bar. Rode back home and it came right off using the breaker bar.

In short, my advice is, make sure you can loosen your fill plug before you drain your oil.
 
#53 · (Edited)
Since my SH was used for an unknown amount of towing by the original owner and I've already towed my little wooden boats over 3k since September, I figure it is past time to change the oil in both the transaxle and rear diff.

After studying most of the threads here I've ordered the gallon size Red Line 75W90 NS GL-5 Gear Oil for the transaxle, but am not sure about the rear diff. Some threads seem to be saying that the read diff should have different oil depending on transmission type, so I'm still confused about the recommended oil.

This thread shows Valvoline full synthetic 75w-90 being used - http://www.subaruforester.org/vbull...-differential-oil-change-2014-fxt-cvt-436642/

Mobil 1 75w-90 has also been recommended, but does is matter if I get LS or not? It only seems to be available in LS.

Thanks!

Edited to add: I got the Mobil 1 LS, so we'll see how that works out.
 
#54 ·
Changed both rear and front diffy fluid in my 2002 Forester 4EAT at 121,700 miles, with Red Line 5W 90 GL-5 Full Synthetic. The rear had some metal filings on the magnet and the color was dark golden brown. Front had about 1/4-inch of sludge and black color. Car running fine. Any reason to be concerned?
 

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