GEE-OTTO Posted December 15, 2010 Share Posted December 15, 2010 Hello fellow Legacy 2.5i owners, this guide will show you how to change your rear differential fluid. Doing this maintenance yourself will help you learn about you car, understand the importance of keeping your fluids fresh, and save you a lot of money over the life of your Subaru. Safety First!!! If you are not mechanically motivated or not even in the same field as mechanical prowess exists, scared to get under your car, scared to touch your Subaru, no idea how to put it on ramps or stands safely, or are just plain not comfortable with this THEN DO NOT DO IT! I take no responsibility for you F-ing up your car or body. This is a 2/10 on the scale of difficulty only because you have to put your car on jack stands or ramps, the other aspects associated with this maintenance are easy. (if you have access to a lift then this will be very easy) Some information: Your rear differential isn't anything mechanically marvelous but you should show it some love every 30K or 60K or 100k miles Your rear differential uses the same fluid as the center/front differential does. Often times you will have enough left over from the front to refill the rear as it take a whopping .8 quarts. Some people say they NEVER change the rear fluid but if for nothing more than to keep the plugs from seizing I would do this simple maintenance. Plus fresh fluid is always better than old broken down fluid and your differential will operate optimally. Questions: Q. GEE OTTO I want to run Shock Proof SAE 140 A. No. Q. Can i use SAE 90 gear oil ? A. Well this is an odd question but in OUR rear differentials (2.5i) you could get away with simple SAE 90 oil. However this wouldn't make much sense, since you will have excess fluid from the front on hand and it calls for 75w-90 per the book/SOA and if you live in a cold climate you may want the cold properties (75w). Q. I thought we had TORSEN rear differentials? A. No Q. Why the filler plug first? I want to drain the differential anyway. A. Well you want to break loose both plugs first then remove the filler, then the drain plug. If you get speedy and take the drain out and don't check to see if the filler will come out, you will have no way to refill the differential unless you tilt your car vertical and you probably don't have a way to do that easily:p Q. Can't I just "bump" the plug with an impact gun if it is seized? A. I generally would not try this ONLY out of fear that if the plug is seized solid (rusted in tight) and you force it out you run the risk of flat spotting the differential case hole thread and that wont be fun to repair. If that did happen i would just put a new rear cover on it. The items you will need: 1/2" Drive Ratchet Two 1/2" drive extensions or one long 1/2" extension1 quart of your choice 75w90 gear oil or the leftover portion of a quart(s) from the front diff fluid changeA catch pan and shop towels Tubing or a fluid pump (to get the fluid in there:))Hammer or mallet (for convincing purposes) Steps: 1.Put your car on ramps or stands or even raise it with a jack so you have access in the rear to the differential. If you use ramps on a hard surface place a rug or rubber mat under it so it doesn't slip when backing up onto it. http://i144.photobucket.com/albums/r182/GEE-OTTO/IMG_0426.jpg It is not a straight shot to the plug the sway bar and frame make it a pain this is why I suggest two extensions swap out the extension and play with combos until you get it with room to work. http://i144.photobucket.com/albums/r182/GEE-OTTO/IMG_0403.jpg 2. Locate the rear differential filler plug and insert the 1/2" drive extension into the square hole with the ratchet (notice the extension combo ) http://i144.photobucket.com/albums/r182/GEE-OTTO/IMG_0428.jpg Now this plug is IN THERE! If your plug is seized spray some PB blaster/WD40 let it sit for 10 mins then try again. Now, you may have noticed that 13 oz hammer in the first pic, if the chemical method didn't work now may be the time to use it, responsibly Tap your ratchet until you feel the plug start to turn then use your manpower to finish. http://i144.photobucket.com/albums/r182/GEE-OTTO/IMG_0436.jpg 3. Locate the drain plug and remove it the same as the filler plug and allow the fluid to drain into your pan: http://i144.photobucket.com/albums/r182/GEE-OTTO/IMG_0430.jpg http://i144.photobucket.com/albums/r182/GEE-OTTO/IMG_0431.jpg 4. While that is draining take a moment to clean up your plugs inspect the threads for flat spots or rung out sockets and replace them if necessary at your dealer: http://i144.photobucket.com/albums/r182/GEE-OTTO/IMG_0432.jpg Can you tell which one is the filler and which is the drain?????? If you mix them up don't fret, they are the same size but the drain is magnetized (top plug in the pic) you want to make sure to put it back in the right hole so it catches the metal shavings from normal wear on the differential, or from when you beat on your car and launch it and expect it to actually launch, as if! So make sure it is put back in the bottom hole of the differential. 5. Replace the drain plug and do not put anti-seize on this plug the fluid itself should prevent that and the fact that you will be doing this on a somewhat regular basis:). Once the plug is in you can start to refill the case. If you have a fluid pump, simply transfer the fluid into the case. I don't have a fluid pump so I used the tubing from the front diff fill and squeezed in the fluid until it started to seep out of the filler hole: http://i144.photobucket.com/albums/r182/GEE-OTTO/IMG_0434.jpg 6. Once the case is full you can put the filler plug back in and tighten it down then take your car off the ramps and you are done. This process takes 30 minutes typically and can be done faster if your plugs aren't stuck. I hope you find this helpful. Link to comment Share on other sites More sharing options...
GEE-OTTO Posted December 15, 2010 Author Share Posted December 15, 2010 I forgot about this but I finally made the thread Link to comment Share on other sites More sharing options...
IanB Posted December 15, 2010 Share Posted December 15, 2010 Now this I can use! Thanks for taking the time! Link to comment Share on other sites More sharing options...
-The Boss- Posted December 15, 2010 Share Posted December 15, 2010 note: Make sure to remove the top plug BEFORE the bottom. If you cant get the top plug out you can refill. Link to comment Share on other sites More sharing options...
GEE-OTTO Posted December 15, 2010 Author Share Posted December 15, 2010 note: Make sure to remove the top plug BEFORE the bottom. If you cant get the top plug out you can refill. In the Q/A section of the thread this is discussed Link to comment Share on other sites More sharing options...
GEE-OTTO Posted December 15, 2010 Author Share Posted December 15, 2010 Now this I can use! Thanks for taking the time! No problem with your 4EAT the front uses Subaru ATF Fluid the dealer has it Link to comment Share on other sites More sharing options...
N.sane Posted December 15, 2010 Share Posted December 15, 2010 Thanks for taking the time to do this Link to comment Share on other sites More sharing options...
GEE-OTTO Posted December 15, 2010 Author Share Posted December 15, 2010 No problem. Link to comment Share on other sites More sharing options...
enaggs37 Posted December 15, 2010 Share Posted December 15, 2010 No problem with your 4EAT the front uses Subaru ATF Fluid the dealer has it Hey GEE OTTO - I also have a 4EAT. Would ATF work for the rear diff too?? Or, do you suggest going with 75w?? I live in Florida for now. But may move back to Northwest based on military obligations. Your thoughts?? Link to comment Share on other sites More sharing options...
N.sane Posted December 16, 2010 Share Posted December 16, 2010 Youll need actual diff fluid. I used Amsoil Severe Gear 75W90 Link to comment Share on other sites More sharing options...
ShrinerMonkey Posted December 16, 2010 Share Posted December 16, 2010 FYI - I have a 2006 2.5i and the rear diff drain and fill bolts are standard 17mm hex bolts instead of the square sockets pictured here. I did have to use my floor jack to break the bolts loose as they were pretty seized after 4 years of Iowa winters. PS - you should try to level the car when doing this instead of just putting the rear on ramps as the diff needs to be level in order to get the proper fill level. I put the front of car on ramps and then jacked up the rear using the diff and put the rear on jack stands to level the car. I was changing the front diff fluid at the same time so this was the easiest method. Link to comment Share on other sites More sharing options...
Chulew Posted January 17, 2011 Share Posted January 17, 2011 Some people say they NEVER change the rear fluid but if for nothing more than to keep the plugs from seizing I would do this simple maintenance. Plus fresh fluid is always better than old broken down fluid and your differential will operate optimally. [/color] Why do some recommend never to change the rear diff fliud? I couldn't find it in the vacation pics plus my 1/2" ratchet turned without the plug once since my filler plug is pretty seized. 131k miles. 1/2" seems a bit loose, is there a specific tool? Link to comment Share on other sites More sharing options...
burnout8488 Posted January 17, 2011 Share Posted January 17, 2011 With 131k I'd say your diff would love you with some new fluid. Generally I thought it was a 60k item, but maybe not. I used a 1/2" ratchet with no issues. Try putting a few layers of masking tape on the ratchet to build up the size of it a little, then crack the ratchet with a dead blow hammer (any BFH) to break the nut free. Link to comment Share on other sites More sharing options...
GEE-OTTO Posted January 17, 2011 Author Share Posted January 17, 2011 Why do some recommend never to change the rear diff fliud? I couldn't find it in the vacation pics plus my 1/2" ratchet turned without the plug once since my filler plug is pretty seized. 131k miles. 1/2" seems a bit loose, is there a specific tool? Well b/c the typical driver wouldn't know that the rear diff is a serviceable component and since the rear diff is a open the minimalist amount of oil is need for medial operation. If the plug is seized and youve rung out the square plug that could be trouble. Try a large Allen key or even a large T bit. Link to comment Share on other sites More sharing options...
soloz2 Posted January 18, 2011 Share Posted January 18, 2011 FYI - I have a 2006 2.5i and the rear diff drain and fill bolts are standard 17mm hex bolts instead of the square sockets pictured here. I did have to use my floor jack to break the bolts loose as they were pretty seized after 4 years of Iowa winters. PS - you should try to level the car when doing this instead of just putting the rear on ramps as the diff needs to be level in order to get the proper fill level. I put the front of car on ramps and then jacked up the rear using the diff and put the rear on jack stands to level the car. I was changing the front diff fluid at the same time so this was the easiest method. I just did this 2 days ago to my 06 2.5i and mine does not have hex bolts. Uses a 1/2" socket extension. 9" for the fill and no extension for the drain is what worked best for me. I did get to see up close how tiny our rear sway bar is though... I'm going to have to do something about that! Current: 16 Crosstrek Premium w/ Eyesight & 05 Outback XT 5MT Past Subies: 14 FXT Premium, 14 WRX hatch, 06 Legacy 2.5i SE 5MT, 98 Outback wagon Link to comment Share on other sites More sharing options...
Chulew Posted January 18, 2011 Share Posted January 18, 2011 With 131k I'd say your diff would love you with some new fluid. Generally I thought it was a 60k item, but maybe not. I used a 1/2" ratchet with no issues. Try putting a few layers of masking tape on the ratchet to build up the size of it a little, then crack the ratchet with a dead blow hammer (any BFH) to break the nut free. Yeah, I figured it would be best to replace the oil. It can only degrade from a new/fresh state. I'll try some tape. A friend suggested a flat head screwdriver wedged in there with the ratchet but with the sway-bar in the way and no lift it was a royal pain in the @$$. So hit it with PB Blaster a few times and will try again or just have a local shop do it. Woulda been nice to have finished while it was up on stands tho. The front oil (5MT) smelled pretty bad but then I've not changed many tranny fluids. Smelled burned. I can sure feel the difference with new 75-90 Royal Purple. Overfilled the front and ended up siphoning the excess out. What is dipstick "notch up" in the service manual? Link to comment Share on other sites More sharing options...
BigBad Posted January 18, 2011 Share Posted January 18, 2011 There is also a nifty little socket tool designed specifically for this I purchased quite some time ago that makes removal of the dif plugs alot easier. http://ultimatetoolco.com/drainplugs.aspx Link to comment Share on other sites More sharing options...
ShrinerMonkey Posted January 18, 2011 Share Posted January 18, 2011 I guess I was lucky and my rear diff plug was a standard 17mm hex. I did have to use my jack to break it loose as it was pretty seized. Diff oil will smell bad as it usually has molybdenum in it that makes it smell sulfurous. Link to comment Share on other sites More sharing options...
soloz2 Posted January 18, 2011 Share Posted January 18, 2011 I'm going to have to try and remember that before I do this again. $30 seems a bit much for a single socket though... Current: 16 Crosstrek Premium w/ Eyesight & 05 Outback XT 5MT Past Subies: 14 FXT Premium, 14 WRX hatch, 06 Legacy 2.5i SE 5MT, 98 Outback wagon Link to comment Share on other sites More sharing options...
Chulew Posted January 20, 2011 Share Posted January 20, 2011 Is brake cleaner ok to flush the rear diff before refilling? I took it to a local lube shop and they charged me $15 to do the rear but before I knew it the guy sprayed brake cleaner in the case and wiped the drain hole out. Then flushed with some gear oil before refilling. It didn't give me warm fuzzies. Is that a common practice? Link to comment Share on other sites More sharing options...
GEE-OTTO Posted January 21, 2011 Author Share Posted January 21, 2011 well the brake cleaner was to get any "gunk" in the carrier housing out and any residual cleaner left was hopefully flushed out by the fluid. I would not worry unless he left the cleaner in there the added fluid as this would be bad and flammable. Link to comment Share on other sites More sharing options...
max Posted January 23, 2011 Share Posted January 23, 2011 If you raise the rear of the car higher, would it mean that you have overflow hole higher as well and you put in too much, or it does not matter. Is the car supposed to be leveled for differential oil change to use overflow hole for oil volume measure? Link to comment Share on other sites More sharing options...
CDN 2.5i Posted January 23, 2011 Share Posted January 23, 2011 Yes, the car should be level when doing this. I did as mentioned earlier by ShrinerMonkey and had the front on ramps with rear on jackstands. Link to comment Share on other sites More sharing options...
GEE-OTTO Posted January 24, 2011 Author Share Posted January 24, 2011 Keep the rear level the easiest way ive ever done it was simply parking over a low spot! At the edge of my driveway the pavement drops off I simply back to the edge (it is still level) and do the change from there, plenty of room! Link to comment Share on other sites More sharing options...
adversexreality Posted January 26, 2011 Share Posted January 26, 2011 Yeah, I figured it would be best to replace the oil. It can only degrade from a new/fresh state. I'll try some tape. A friend suggested a flat head screwdriver wedged in there with the ratchet but with the sway-bar in the way and no lift it was a royal pain in the @$$. So hit it with PB Blaster a few times and will try again or just have a local shop do it. Woulda been nice to have finished while it was up on stands tho. The front oil (5MT) smelled pretty bad but then I've not changed many tranny fluids. Smelled burned. I can sure feel the difference with new 75-90 Royal Purple. Overfilled the front and ended up siphoning the excess out. What is dipstick "notch up" in the service manual? diff fluid always has a sort of burning smell.. trust me i know because i was expecting to smell OIL LOL what an idiot I make T-Shirts! and I Detail Cars(I'll go to you!) Send me a PM!! Link to comment Share on other sites More sharing options...
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