I have read a little information on this issue, but what I am curious about; how critical is this?
The reason I am asking is because I first noticed it when I took a trip to Milwaukee this spring (~100 miles). Half way there I stopped at a rest stop and heard this clunk as I pulled into the slanted parking spot. It was difficult to tell if it was coming from the front or rear. Since I had a plane to catch and there was no issue driving normally, it just happened when turning fairly sharply which is only done at reasonably slow speeds, I continued to the airport. At the airport it happened again as I pulled into a slanted parking spot.
When I returned from the trip 10 days later, there was no issue when I left the airport. I drove the ~100 miles home and it happened again as I turned into my driveway. Again I could not tell if it was front or back. The next day, no problem.
Over the course of the summer, I only noticed it when the vehicle had been driven for 20-30 minutes, highway or city. I changed the rear diff oil and the sound tended to get softer at first, then returned to its previous level. I changed the manual transmission oil and again the sound got softer at first then over time it returned to the previous level.
Now fall is here, temperatures are lower and I noticed it takes longer during city driving to generate the sound/clunking.
If it has to be replaced, I would prefer to wait until spring since the colder temperatures will probably generate enough cooling that it won't be an issue unless I take a reasonably long trip 50+ miles or more. Possible, but not likely under the circumstances.
At the start I asked how critical this was. I would also like to ask if there is any other solution? Since changing the oil on the rear diff and the manual transmission seemed to have some impact, I am curious if there is any other option available?
I appreciate anyone's thoughts on this. Thanks.
Center Differential
Moderator: bajabob
Re: Center Differential
I did mine about 10 months ago, or had a shop do it. the Cen diff. is at the end of the transmission. from what I have read, the trans. does not have to be pulled for it to be changed, but some shops like to put the whole tranny on the bench, for easier access. just so they dont have to work with it over head. the part itself cost about $690. It is a Subaru part and there are no aftermarket manufactures.
to answer your first question: If the center diff goes out, I believe that you will ultimately loose power to the rear wheels. the tranny transfers the power through the center diff, turning the propeller shaft which then powers the rear wheels.....i think. So with that being said, I could not stand the front end cluck, because I thought the front was going to come off. I did take it to the subaru dealer, in San Antonio, and they are genuine fuck-ups. They did not even diagnose it correctly after I already knew what it was.
I had a local shop do it. $1220 which included tax.
a big hit to the wallet, but I am happy with the results.
good luck.
to answer your first question: If the center diff goes out, I believe that you will ultimately loose power to the rear wheels. the tranny transfers the power through the center diff, turning the propeller shaft which then powers the rear wheels.....i think. So with that being said, I could not stand the front end cluck, because I thought the front was going to come off. I did take it to the subaru dealer, in San Antonio, and they are genuine fuck-ups. They did not even diagnose it correctly after I already knew what it was.
I had a local shop do it. $1220 which included tax.
a big hit to the wallet, but I am happy with the results.
good luck.
Re: Center Differential
Thanks much for your response mowillie. Your original post was the one that made me realize that was the issue. Before that I did not even realize there was a center differential. Of course now it makes sense.
I may be able to get a used diff. and I do have access to a pretty good maintenance company. They replaced my drive side front shaft after the boot split for a reasonable price - $225. So I am hoping I can beat that $1200+ cost to you. No guarantees though.
In the meantime I am still confused why I can change the oil for the rear diff and in essence the front diff via the manual transmission oil, but I can't maintain the center diff. It seems odd that it would rely on simply the oil from the transmission (or rear diff.).
Anyone have thoughts on alternative maintenance options? It is not just to buy time for this one, but I would like to keep this vehicle at least until I hit 200K. So even if I replace the center diff., I want to maintain it better this time.
By the way, I forgot to mention the vehicle is an 05 Baja Sport. It had 90K miles when this first started to occur. Since I do a lot of bike riding in the summer, it only has 94K miles now.
Thanks for any insight you can give me.
I may be able to get a used diff. and I do have access to a pretty good maintenance company. They replaced my drive side front shaft after the boot split for a reasonable price - $225. So I am hoping I can beat that $1200+ cost to you. No guarantees though.
In the meantime I am still confused why I can change the oil for the rear diff and in essence the front diff via the manual transmission oil, but I can't maintain the center diff. It seems odd that it would rely on simply the oil from the transmission (or rear diff.).
Anyone have thoughts on alternative maintenance options? It is not just to buy time for this one, but I would like to keep this vehicle at least until I hit 200K. So even if I replace the center diff., I want to maintain it better this time.
By the way, I forgot to mention the vehicle is an 05 Baja Sport. It had 90K miles when this first started to occur. Since I do a lot of bike riding in the summer, it only has 94K miles now.
Thanks for any insight you can give me.
Re: Center Differential
Mine had 64k on it when i had it replaced. The previous ownern claimed he knew nothing about the issue...yeah right. 
Well it was my problem since i bought the car from an individual and wanted it fixed since i like the car.
So i am no expert on the center diff. but this is what i beleive happens. Most deals with tires. Keep them inflsted to the recommended psi. Never let one drop down. If you get a flat tire, NEVER use the spare. Since our cars are AWD, the smaller donout tire changes the dynamics of the axels, rack and pinions, drive train, etc... a smaller tire has to make more revolutions to keep up with the other three. It cost more but you should have it flat towed to a tire shop. Or what i do is take the tire off, have my wife pick me up and drive me to the shop, fix it and put it back on....i know, its all a pain in the ass but cost less than a center diff.
Also, if you need a new tire, you should buy four new ones...same size and tread. There are slightly size differences in same size tires of different brands. Enough to make difference rotation distance. If you replace just two, and the other two are a couple years old, too much difference in size.
I know it may sound like its a little over-doing-it, but it all cost less than a center diff.
One other thing is dont do donouts in the parking lot. Screws up the center diff.
As far as getting a used one. You have no clue how it was treated in the donor car. I say, suck it up, buy it new get it done right the first time and then baby your car from then on.
Well it was my problem since i bought the car from an individual and wanted it fixed since i like the car.So i am no expert on the center diff. but this is what i beleive happens. Most deals with tires. Keep them inflsted to the recommended psi. Never let one drop down. If you get a flat tire, NEVER use the spare. Since our cars are AWD, the smaller donout tire changes the dynamics of the axels, rack and pinions, drive train, etc... a smaller tire has to make more revolutions to keep up with the other three. It cost more but you should have it flat towed to a tire shop. Or what i do is take the tire off, have my wife pick me up and drive me to the shop, fix it and put it back on....i know, its all a pain in the ass but cost less than a center diff.
Also, if you need a new tire, you should buy four new ones...same size and tread. There are slightly size differences in same size tires of different brands. Enough to make difference rotation distance. If you replace just two, and the other two are a couple years old, too much difference in size.
I know it may sound like its a little over-doing-it, but it all cost less than a center diff.
One other thing is dont do donouts in the parking lot. Screws up the center diff.
As far as getting a used one. You have no clue how it was treated in the donor car. I say, suck it up, buy it new get it done right the first time and then baby your car from then on.
Re: Center Differential
Where did you 'read up' on this 'issue?'
The symptom given (metallic clunk when turning is what I got from the LIMITED description) does not align well with a failing center differential. It better (best?) aligns with a CV joint that needs to be replaced.
But wait, there's more. Most Subarus with A/Ts don't have an actual differential in them. All they have is a clutch pack at the tail end of the tranny that is pressurized to a greater or lesser degree, according to what the TCU directs. The clutch pack is very, very much like every other clutch pack in an A/T. The VTD center diffs (in the turbo Bajas, at least in '05 and '06, for example) are entirely different. They're a planetary gear set.
Manual transmission Subies, however (speaking of newer-gen models like the Baja), have an actual, genuine mechanical differential in them, just like the rear diff. It simply has basically a limited slip clutch pack in it, though that system is a viscous system which does NOT share fluid with the rest of the tranny. It's a silicon fluid and the system locks as the fluid heats up (which happens because of the shear involved when the clutch pack slips). Here's a decent explanation of how the viscous coupling works: http://www.awdwiki.com/en/Viscous+coupling/. A pretty decent overall Subaru tranny page is at: http://www.awdwiki.com/en/subaru/.
So, since you have an M/T Baja, if your center differential failed it'd need to be replaced because, just like if the rear diff failed, drive power would be lost. However, that'd be a mechanical failure that plain and simply NEVER happens to Subies (obviously it could happen, but really and truly it NEVER does). If, on the other hand, it was just a failure of the viscous coupling, you'd merely have an open center differential. No particular symptoms associated with that other than possibly getting stuck in snow banks, mud, or deep sand more easily.
So, I urge extreme caution in jumping to the conclusion that your M/T's center diff is broken. EXTREME caution. 99.99% probability is that is isn't. If the viscous coupler has failed, first of all it's probably failed 'locked' such that you have driveline binding. If that's the symptom you're trying to describe, okay. It just didn't/doesn't read that way to me. It's your decision whether to replace it or not, but a junkyard part is way less expensive.
You might want to check on the USMB for further technical information on this topic. There is some good information at this link, too, which you may have already seen: http://www.subaruforester.org/vbulletin ... hem-46979/
The symptom given (metallic clunk when turning is what I got from the LIMITED description) does not align well with a failing center differential. It better (best?) aligns with a CV joint that needs to be replaced.
But wait, there's more. Most Subarus with A/Ts don't have an actual differential in them. All they have is a clutch pack at the tail end of the tranny that is pressurized to a greater or lesser degree, according to what the TCU directs. The clutch pack is very, very much like every other clutch pack in an A/T. The VTD center diffs (in the turbo Bajas, at least in '05 and '06, for example) are entirely different. They're a planetary gear set.
Manual transmission Subies, however (speaking of newer-gen models like the Baja), have an actual, genuine mechanical differential in them, just like the rear diff. It simply has basically a limited slip clutch pack in it, though that system is a viscous system which does NOT share fluid with the rest of the tranny. It's a silicon fluid and the system locks as the fluid heats up (which happens because of the shear involved when the clutch pack slips). Here's a decent explanation of how the viscous coupling works: http://www.awdwiki.com/en/Viscous+coupling/. A pretty decent overall Subaru tranny page is at: http://www.awdwiki.com/en/subaru/.
So, since you have an M/T Baja, if your center differential failed it'd need to be replaced because, just like if the rear diff failed, drive power would be lost. However, that'd be a mechanical failure that plain and simply NEVER happens to Subies (obviously it could happen, but really and truly it NEVER does). If, on the other hand, it was just a failure of the viscous coupling, you'd merely have an open center differential. No particular symptoms associated with that other than possibly getting stuck in snow banks, mud, or deep sand more easily.
So, I urge extreme caution in jumping to the conclusion that your M/T's center diff is broken. EXTREME caution. 99.99% probability is that is isn't. If the viscous coupler has failed, first of all it's probably failed 'locked' such that you have driveline binding. If that's the symptom you're trying to describe, okay. It just didn't/doesn't read that way to me. It's your decision whether to replace it or not, but a junkyard part is way less expensive.
You might want to check on the USMB for further technical information on this topic. There is some good information at this link, too, which you may have already seen: http://www.subaruforester.org/vbulletin ... hem-46979/
Re: Center Differential
Thanks again mowillie. Other than an obsessive attention to the 4 tire psi, the rest I do. All 4 tires were replaced at 60K, and none of the 4 show more wear than the others. Tis true on the used one diff, but it would depend on the price, age and miles to see if it was worth the risk. The fact that yours went at 64K increases the risk of a used one. I would not have expected one to start failing that early.
However, I think doing a little more research using the links bulwnkl provided is definitely worth the time. I have not had the chance to start them yet, but no matter what they should be educational and worth the time. Like I said, I want to keep this vehicle for many more miles, so figuring out the right thing is worth the time.
Now I have to check the cv joints as a check point, but the last time I checked them I could not find anything wrong. Then move on to the limited slip center diff (assuming I understood bulwnkl correctly) and the viscous coupling literature. That may be the problem, and if I understand him correctly although he didn't state this explicitly, they might all be replaced with the center diff which could be overkill.
If I am not understanding you correctly bulwnkl please don't hesitate to correct me. Understanding is the key to knowledge.
Thanks very much to both of you for your insight, and please don't stop if you have more.
However, I think doing a little more research using the links bulwnkl provided is definitely worth the time. I have not had the chance to start them yet, but no matter what they should be educational and worth the time. Like I said, I want to keep this vehicle for many more miles, so figuring out the right thing is worth the time.
Now I have to check the cv joints as a check point, but the last time I checked them I could not find anything wrong. Then move on to the limited slip center diff (assuming I understood bulwnkl correctly) and the viscous coupling literature. That may be the problem, and if I understand him correctly although he didn't state this explicitly, they might all be replaced with the center diff which could be overkill.
If I am not understanding you correctly bulwnkl please don't hesitate to correct me. Understanding is the key to knowledge.
Thanks very much to both of you for your insight, and please don't stop if you have more.