shortskoolbus Posted May 12, 2009 Share Posted May 12, 2009 Did a search for this but didn’t have much luck. Is it difficult to remove and replace the rear differential? I just pulled my 4EAT a few weeks ago, so I had all the tools needed to do that, I’m assuming that should be adequate for this job. I just picked up a used rear diff off of Ebay. Looking at the FSM it looks like a lot of steps to swap the rear differential though. I have a few questions after looking at the FSM: 1) How do I get the rear drive shafts out of the diff? The FSM calls out some special tool. 2) FSM says to replace the side seals, is this pretty straight forward? Take out old seal, drive new seal in? I can do it on the new diff while it is out of the car i assume. It also has some special tools to “protect” the seals when re-installing drive shafts... will that be necessary? 3) Do i really need to remove the propeller shaft? i don't want to drop the exhaust if i don't have to... the bolts at the different sections are all rusted together so i have to drop it in two big rump roast pieces or end up breaking a bunch of bolts.. thats a real PITA. Any other tips? Thanks, Quote Link to comment Share on other sites More sharing options...
erik litchy Posted May 12, 2009 Share Posted May 12, 2009 yeah grab some Kroil for bad bolts. sounds like you want to replace the innards rather than the whole unit. thats a bit more ambitious than changing the transmission out. Quote Link to comment Share on other sites More sharing options...
shortskoolbus Posted May 12, 2009 Author Share Posted May 12, 2009 No i just plan to do a direct swap. The diff i just bought for the bad diff on my car Quote Link to comment Share on other sites More sharing options...
Gnuman Posted May 12, 2009 Share Posted May 12, 2009 How about model and year so we can help better? I'm fairly familiar with the drive gear on anything up to about 2000 and could likely look at a picture to see if the later ones are different. . . Some things to consider are if the diff matches your 4EAT. look at teh final ratio on the tranny and the diff ratio to see if they are the same. If they are not the same, you will get into trouble big time. As for removing the propeller shaft, you have to be able to swing it clear of the diff to get eh diff out. if you cannot do this, you will need to remove at least the rear half of the shaft. I recomend that you break all the nuts and bolts loose before taking any all the way off. You would not believe what an unholy *(&^(*&^ it is to have just one nut you need to get loose and the diff is swinging about as you try to break it loose. . . nah, I havn't been there. Why do you ask? Quote Link to comment Share on other sites More sharing options...
shortskoolbus Posted May 12, 2009 Author Share Posted May 12, 2009 Oops, some how i thought the year and model of my car would show up from my profile. Its a 97 Legacy L Wagon 4EAT. The diff should be the right one, it was advertised as fitting 95-99 Impreza/Legacy 4EAT. I just dont know how difficult it's gonna be. My mechanic will do it for $200, but if its not a big job i'd rather just do it myself. But the last thing i did myself (rear main) i apparently screwed up pretty bad :-\ Quote Link to comment Share on other sites More sharing options...
bheinen74 Posted May 12, 2009 Share Posted May 12, 2009 why do you think your rear diff is bad, they rarely ever go bad, but rather a lot of times torque bind, etc, shutter, people think it the rear diff, but it is really the rear clutchpacks, center diff of the tranny..... you might be in a world of hurt with this " it was advertised as fitting 95-99 Impreza/Legacy 4EAT." yeah, it will fit, but might not have the correct drive ratio......you need to post more info on here, BEFORE you ruin a tranny or something else. Quote Link to comment Share on other sites More sharing options...
Gnuman Posted May 12, 2009 Share Posted May 12, 2009 I'm with bheinen74 on this. Being AWD, your car has two differentials, One in the front that looks like part of the tranny, and one in the rear, that looks like any RWD diff. The ratios on these two differentials have to match, or you will damage the AWD mecanism of your transmission. It will physically fit, but that is only half the story. let's first be sure that it is the right diferential, then we will help you get it into the car. First things first: is the tranny original to your car? If not, what is it out of? Do you know the final ratio of the tranny? Next, do you know the final ratio of the Diff? There may be a sticker on the back to tell you what this ratio is. Quote Link to comment Share on other sites More sharing options...
shortskoolbus Posted May 12, 2009 Author Share Posted May 12, 2009 why do you think your rear diff is bad, they rarely ever go bad, but rather a lot of times torque bind, etc, shutter, people think it the rear diff, but it is really the rear clutchpacks, center diff of the tranny..... you might be in a world of hurt with this " it was advertised as fitting 95-99 Impreza/Legacy 4EAT." yeah, it will fit, but might not have the correct drive ratio......you need to post more info on here, BEFORE you ruin a tranny or something else. I know the rear diff is bad because i am getting a pretty bad howl and chatter from the rear. I listened to it with a stethescope and it is definitely coming from the differential. I've heard that they rarely fail, so I ruled out all options including listening to the wheel bearings with a stethescope and making sure no play in the drive shaft. Quote Link to comment Share on other sites More sharing options...
shortskoolbus Posted May 12, 2009 Author Share Posted May 12, 2009 I'm with bheinen74 on this. Being AWD, your car has two differentials, One in the front that looks like part of the tranny, and one in the rear, that looks like any RWD diff. The ratios on these two differentials have to match, or you will damage the AWD mecanism of your transmission. It will physically fit, but that is only half the story. let's first be sure that it is the right diferential, then we will help you get it into the car. First things first: is the tranny original to your car? If not, what is it out of? Do you know the final ratio of the tranny? Next, do you know the final ratio of the Diff? There may be a sticker on the back to tell you what this ratio is. The tranny is original to the car, I havent recieved the rear differential yet, so I will have to check. How can i check the ratio of the tranny? I thought there was only one gear ratio for the 2.2L 4EAT which is 4.111? Unless that's not the same as the drive ratio... You guys are worrying me. Quote Link to comment Share on other sites More sharing options...
shadetreemech Posted May 12, 2009 Share Posted May 12, 2009 I did a rear diff swap on '95 SVX. I swapped in a '97 4EAT trans (4.44 final ratio) from a legacy outback, and had to swap in a salvage outback diff to match the 4.44 trans ratio. (and I had to change out the diff spider to keep the LSD function) You need to just suck it up and get the exhaust out of the way so you can do the work and see what is up there. On the SVX, I unbolted diff from the chassis and lowered it down with a jack. As the diff is lowered, clearance is developed to allow the axles to be removed. The axles slip off the differential stubs if you drive out the pins first. The side seals are mounted in aluminum alloy side plates, so it is best to get the unit on the bench and see what you really have. Use new o-rings to seal the side plates when you reassemble. If you do pull the side plates, you will find some shims under them. These shims set gear clearances inside the diff, so put them back the same way they came out. good luck. Quote Link to comment Share on other sites More sharing options...
idosubaru Posted May 13, 2009 Share Posted May 13, 2009 there are two possible gear ratios, make sure it matches. don't bother worrying about year/models, just check it to be sure. rotate and count revolutions. there's 3.9, 4.11, and 4.44. rear differentials are REALLY easy to replace. did you say you did a transmission? rear diffs are cake compared to that. no special tools needed at all. each model,trans, engine, etc has slight variations but you can just unbolt the 4 bolts at the rear diff where the driveshaft attaches. then it's completely free from the diff, no need to mess with the rest of the driveshaft, pulling it from the trans or the exhaust in the way. i haven't done a legacy but in the past i've dropped the diff, leaving it still connected to the axles and then that gives enough room to work the axles off. on the old school diffs there were only 3 bolts holding the diff in place. so remove those and the 4 12mm driveshaft bolts and you're done except the axles. PB Blaster, Liquid Wrench or whatever your favorite penetrant is for those rusty driveshaft bolts. They're not all that tight, so spray them and they should come off. Make sure to use a good SIX POINT wrench on them, not a 12. If you have a torch, hit the nut real quick then bust it loose right away just for good measure. Quote Link to comment Share on other sites More sharing options...
shortskoolbus Posted May 13, 2009 Author Share Posted May 13, 2009 there are two possible gear ratios, make sure it matches. don't bother worrying about year/models, just check it to be sure. rotate and count revolutions. there's 3.9, 4.11, and 4.44. rear differentials are REALLY easy to replace. did you say you did a transmission? rear diffs are cake compared to that. no special tools needed at all. each model,trans, engine, etc has slight variations but you can just unbolt the 4 bolts at the rear diff where the driveshaft attaches. then it's completely free from the diff, no need to mess with the rest of the driveshaft, pulling it from the trans or the exhaust in the way. i haven't done a legacy but in the past i've dropped the diff, leaving it still connected to the axles and then that gives enough room to work the axles off. on the old school diffs there were only 3 bolts holding the diff in place. so remove those and the 4 12mm driveshaft bolts and you're done except the axles. PB Blaster, Liquid Wrench or whatever your favorite penetrant is for those rusty driveshaft bolts. They're not all that tight, so spray them and they should come off. Make sure to use a good SIX POINT wrench on them, not a 12. If you have a torch, hit the nut real quick then bust it loose right away just for good measure. Thanks. Actually driveshaft bolts are in great shape. I had the driveshaft off for the tranny already anyway. I'm just a little concerned because it's a lot of steps in the FSM. And now i'm also concerned whether or not i have the right ratio... Quote Link to comment Share on other sites More sharing options...
idosubaru Posted May 13, 2009 Share Posted May 13, 2009 i've removed more trans and rear diffs than i know and i can say the rear diff job is straight forward and easy compared to a transmission. not even a comparison, you'll be fine. if anything, it's nice to have a helper since it is heavy enough to be awkward in odd positions. but even still i've always done them by myself. that being said - make sure there isn't an easier way than the FSM is showing, often times the FSM shows more steps than necessary. i'm not up on the EJ procedure from memory so i can't fill you in off the top of my head. Quote Link to comment Share on other sites More sharing options...
Gnuman Posted May 13, 2009 Share Posted May 13, 2009 There are two types of rear diff for EJ series transmissions. One has roll pins on axle stubs like the front diff has, and on the other, the halfshaft pulls out of the diff. Inspect before you start. Also drain the diff before you start to avoid getting a faceful of gear oill. That stuff is nasty! I start by putting the car up on jackstands and pulling the propeller shaft (disconnect it at the rear diff. If it moves far enough out of the way that you can clear it, good. Otherwise, also pull the 4 bolts from just behind the center bearing. That is all the space you will need) Next loosen the 14mm boltsfrom around the rock shield that protects the rear diff as well as the two hanger nuts on the rear. take the shield off and put a jack under the diff for safety. If yoru diff is the type with the roll pins, you should have removed them by now. If not do so now. If you have the type that does not have roll pins, get a big pry bar. with the rock shield off, you should have 6(?) bolts to remove before you can lower the diff. Again, loosen them first to avoid complications later. Lower the diff just a bit so you can shove it off to one side and tilt it enough to pull one halfshaft out. Once you have one side free, you can pull the other side free and the diff is out of the car! That may sound like a lot, but it really isn't. There are about twice as many steps to getting the 4EAT out and you have already done that. . . . Quote Link to comment Share on other sites More sharing options...
shortskoolbus Posted May 13, 2009 Author Share Posted May 13, 2009 (edited) Thanks Guys. Sounds easier than i thought. The FSM had included a bunch of steps like loosing the handbrake cable clamps and the front member mounting points, etc. Actually i think it says to remove the whole rear diff with the front member still attached to the car... How do i know what the drive ratio is for my transmission? Also, is it necessary to replace the side seals before i put the new (used) diff back in? Edited May 13, 2009 by shortskoolbus Quote Link to comment Share on other sites More sharing options...
edrach Posted May 13, 2009 Share Posted May 13, 2009 (edited) How do i know what the drive ratio is for my transmission? Also, is it necessary to replace the side seals before i put the new (used) diff back in? There's an ID label on the transmission bell housing near the starter motor. On a manual tranny the ID # is something like TY-752-VC1AA; that number will match the transmission number on the VIN plate mounted on the driver's side inner fender. Check the transmission information in the USRM to identify the front diff ratio. http://www.ultimatesubaru.org/forum/showthread.php?t=97885. The chart lists mainly manual transmissions; there has to be one for automatics. You mention you have a FSM; check the transmission and rear diff sections to get info. I have a FSM for my '97 Impreza and it indicates the the automatic front diff ratio is 4.111. It also indicates that the is an ID stamped in the rear housing of the rear diff. It runs vertically between the two vertical bolts on the left side. For an EJ22 equipped automatic the rear diff is identified by VA1REF-XG and would be 4.111. Remember this is an Impreza FSM. I don't know if the Legacy is the same. I don't think it's necessary to replace the side seals unless they are leaking already. Edited May 14, 2009 by edrach Quote Link to comment Share on other sites More sharing options...
shortskoolbus Posted May 14, 2009 Author Share Posted May 14, 2009 You mention you have a FSM; check the transmission and rear diff sections to get info. I have a FSM for my '97 Impreza and it indicates the the automatic front diff ratio is 4.111. It also indicates that the is an ID stamped in the rear housing of the rear diff. It runs vertically between the two vertical bolts on the left side. For an EJ22 equipped automatic the rear diff is identified by VA1REF-XG and would be 4.111. Remember this is an Impreza FSM. I don't know if the Legacy is the same. I don't think it's necessary to replace the side seals unless they are leaking already. Thanks. Well actually i thought the FSM was pretty clear the drive ratio i'm looking for is a 4.111. This is for the transmission: This is for the differential: But based on the information in this thread it made me doubt if those tables are 100% correct... such as there might possibly be some known variations not documented in the FSM. Quote Link to comment Share on other sites More sharing options...
Gnuman Posted May 14, 2009 Share Posted May 14, 2009 Is the top chart 4EAT specific? If so, tehn the 4.111 is the ratio you need it to be. There should be a sticker on the rear of the diff to say what the ratio of the diff is. As for replacing the seals, the choice is all yours. In favor of it is the fact that this used diff that you are getting has a history that you know nothing about. you do not know if it leaks at the seals or not. Replacing them would make sure. On the downside, do you really want to mess with the seals if you don't have to? One point of advice: if the seals leak after you put the diff in, you *can* replace them with the diff in the car. Quote Link to comment Share on other sites More sharing options...
shortskoolbus Posted May 14, 2009 Author Share Posted May 14, 2009 Is the top chart 4EAT specific? If so, tehn the 4.111 is the ratio you need it to be. There should be a sticker on the rear of the diff to say what the ratio of the diff is. As for replacing the seals, the choice is all yours. In favor of it is the fact that this used diff that you are getting has a history that you know nothing about. you do not know if it leaks at the seals or not. Replacing them would make sure. On the downside, do you really want to mess with the seals if you don't have to? One point of advice: if the seals leak after you put the diff in, you *can* replace them with the diff in the car. Yup, top chart is for the 4EAT only Thanks for all of the advice. Just gotta wait for the diff to get in now! I'm sure i'll be back here when i get stuck taking that thing out, its never as easy at it sounds. Quote Link to comment Share on other sites More sharing options...
shortskoolbus Posted May 14, 2009 Author Share Posted May 14, 2009 Oh one more question, do the tires need to be free to do this job? Or can i put the back on ramps? i'm never that comfortable under jackstands.. Quote Link to comment Share on other sites More sharing options...
shortskoolbus Posted May 18, 2009 Author Share Posted May 18, 2009 Okay need some help now. I got the diff lowered, but how do i get the rear axles out? There aren't any spring pins like the front axles.. Quote Link to comment Share on other sites More sharing options...
marinemedic Posted June 12, 2009 Share Posted June 12, 2009 I replaced the whole housing on my 96 impreza I rented lift time from a friend and in his shop it took me 6 hours I also live in upstate NY with rust the lower bolts that hold the rear trailing arms to the knuckles were froze I had to take trailing arms from frame to get the axles out ... When I opened the diff the spider gears were shattered Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.