jhelm_waterw

Wow... this is an old thread but I am having the exact same symptoms in my 2001 Outback. It's totally unpredicitable when it works and when it does not. It seems the compressor is just not kicking in. I hit the A/C button, it goes green, the idle gets bumped up a bit but you can tell the compressor is not engaging. Then other times, works like a champ. I'll have to see if the compressor is getting the correct control voltage.

Yep... you are correct Nipper. Actually, (if I am not mistaken) Lexus uses a computerized version of this trick for it's traction control. The Lexus rear does not use an LSD, so if the system (probably the same exact wheel speed sensors that are used as feedback to the ABS) senses one of the wheels spinning much more than the other, it applies brakes to the slipping wheel to redirect power to the other wheel. But us poor folks just stomp on the brake pedal.

You do sort of have a 2wd. The center differential is a LSD and it is the thing that directs power to the front and rear. However... neither your rear nor your front has its' own LSD. So... if one of your front tires is slipping and one of your back tires is slipping, you are not going anywhere. Either the front or the back must have both tires gripping or the system fails.

Wrong. Lots of 5 speed trannys get the VC torque bind problem. I know of 3 friends who have had it. You only need to overheat your center differential once to get it to start behaving poorly. And it cannot be fixed by just putting in new diff fluid. The OIL that you add to your gearbox is NOT the fluid that is INSIDE your VC. The VC is a sealed and pressurized unit with a proprietary fluid (that I could not get even through my man at subuaru headquarters in NJ) Trust me.. it would take you or me about $10k worth of equipment to properly repair a VC. For a shop (like the one in austrailia that monkeys with WRX's transmissions) they already have that equipment and can probably play with 50 different hydraulic fluids and see which one works best and bench test it. You and me should just bite the bullet and buy and new or gently used one. HOWEVER... having said that... if you DO have a going-bad VC AND your gearbox is low on oil, adding oil to the gearbox MAY help (a little) due to the cooling properties. When the VC is on its' way out, it gets very sensitive to heat (which is why it behaves when the car is cold and gets worse as you drive, especially in arizona). So checking your gearbox oil is ALWAYS a good thing and MAY help extend the VCs imminent failure, but it aint gonna fix it.

Ferret, I liked your reply. I am having my own cylinder 4 misfire issue also. My question is this: how does the computer (ECU) detect a successfull detonation? (What sensor or mechanism tells the computer that a cylinder fired off?) It's not like there are 4 individual cylinder head sensors on the system. (and just because a spark plug itself did fire, does not mean there was a viable cylinder combustion) Thanks in advance for any insight.

Hawksoob, $921 ? Yowee..... Ok, if that is how much it costs, that is how much it costs. Yeah... your tranny should be good for at least another 150K. Did they give you the old VCU? Can you get it? I can give you a few bucks for it (like $50 plus shipping?) I am on a mission. I want to get a 'bad' one and crack it open. I am willing to blow $50 just to see how these things tick. Whadya think? Can you ask the mechanic for the spent unit? I have some theories about these things that I need to test. Thanks Jeremy p.s. email me !

WRX, you wrote: 'I thought when vcenter diff goes out when its a viscus, it just acts like a open diff'. I know what you're thinking. I thought the same thing initially. That is what I would guess would be the case but it is, judging from all the posts, talking to mechanics and my current experience, not the way they fail. They all seem to definitely become very sticky first (possibly for a VERY long time) then they eventually fail completely and go 'Open'. I have conversed with MB users who talk about them going on like this for years before eventually failing. I could sort of deal with the nuisance of the scrubbing when parking the car but this has got to induce rediculous stress on all the remaining parts of the drive line. Could you imagine driving around, on dry pavement, with an old 'switch on the fly 4WD' turned on all the time??? That is what it feels like sometimes (when it's warm & I've driven it a while). Also, I wish I could swap the part out with a WRX part. But you are lucky in that your center differential is the new kind that bolts onto the back of the tranny. You do not have to remove your entire tranny to fix it. Mine, unfortunately is buried inside the main tranny case so I have to remove & disassemble the whole unit. Thinking back, I probably know exactly when I damaged this unit. I was in Killington leaving a bar (sober!) at 2 in the morning when it was -20F out. I was trying to leave up a hill and had my jacket over the emer brake and did not realize it was fully on. I just gunned the mutha thinking I was having a hard time on the hill. It also turns out I was in 3rd gear at the time (from a stand still on a hill), but the tranny was so frozen and hard to shift I really thought I had it in first. My clutch almost burnt up entirely and stank up the car. There was also another stank I did not recognize. It had to be the gearbox. Really, my car smelled like a fire for 2 weeks. One moment of stupidity... $$$ worth of repair.

George, Thanks for the reply. Your 99 Forester has the 'bolt on the rear' differential? Yeah.. on my make/model the VC Center diff is buried inside my tranny housing and I have to take it down & apart to get to it. I read the entirety of your thread and found it informational but I disagree with a few people who posted there. This is my GUESS/OPINION ONLY. I definitely understand the proposed theory that if this unit was to fail it would fail OPEN. (much like a burnt out clutch) ie. no power being transfered to the rear wheels. However, I do not think this is quite as linear a failure. I think this is a two-step failure. I believe it starts by overheating the unit (like me pulling snowmobiles) and thus burning off or gumming up some of the precious silicone. This is only the start of the problem. Now, the viscosity has radically changed and the unit starts binding as soon as it gets slightly warm. This, in turn, causes way too much daily friction and, in turn, burns off even more fluid and, in time, ruins the disks. Then, one has an 'OPEN' failure. My little theory on 'why' they fail may be off-target, but everyone with whom I've conversed about this problem seems to recognize the first stages of the failure to be the dreaded '4WD scrubbing/binding' to be followed much later by complete failure. BTW, did that other guy ever get back to you with where his mechanic found a Center diff for $250??? Thanks again. jeremy

Hawksoob... Where did you see it online for $401 ? I am planning on pulling my tranny anyway when I replace the clutch and I am more than willing to crack that walnut to drop in a new differential. I dunno... I was even thinking of just drilling a FREAKIN hole in the side of the differential, adding some hydraulic fluid and mig welding the hole closed. Then maybe bench test it on a metal lathe as they discuss in an article I found online. Somebody out there has to have tried this. I can't be the only idiot on the planet who doesn't want to shell out $400+ for a new part.

Hi all and thanks for reading. I have a 96 2.2 AWD Legacy Wagon with a 5 speed which means it uses the viscous coupled center differential. Only in the last few months, I have been experiencing the '4WD Scrub' which means it binds up and shudders when turning a corner (Like my old switch on the fly locking 4WD Loyale) This does not happen when the car is cold, only when I have been driving it for a while (once it is warm/hot). So... the magic silicone fluid that fills the center diff is getting hot and binding even when it should not. I have all new matched tires which means that is not the problem. I'm pretty sure I have just burned off/overheated too much of that fluid or beaten up my center diff towing too many heavy toys. I was told 'Yep, it is shot. You cannot fix it, just buy a new one ($450). You have to drop the tranny, pull it apart and replace the diff as a whole unit' Is this true? Has anyone heard of this? I have SEARCHED the net and come up with very few answers. No one really talks about the viscous center diffs. Can I replace/refill the silicon fluid? Are these servicable ? Can I buy a used one? Where? Thanks a lot in advance, Jeremy