Need help diagnosing my AWD problem

[uberpixel]

Hello. I need help figuring out why my Subaru is not acting like a Subaru.

We are experiencing our annual snowstorm here in Portland Oregon. This means that the roads are clogged with idiot drivers and the world is coming to an end.

That said, I have successfully navigated the snow covered streets in my 95 Legacy L. The snow has provided me with the opportunity to test something that I have long suspected (since shortly after I bought the car used from a dealership a few years ago) - I don't think my AWD works.

What I have observed is that only the front wheels spin on slick surfaces. I tested this last night on some ice. While looking out the driver's side door only the front wheel was spinning. I did this test in "D" and in "1" and "2". Same results - rear wheels do not turn. I've driven other AWD vehicles (Chrysler minivan) and know what proper AWD is capable of. There is something wrong with my Subaru.

I checked the 2WD switch - there is no fuse present so it is not activated. I've been reading about solenoids and the multi-plate clutch but I haven't read anything about them ever failing...

Based on my observations can anyone help me figure out what is going on?

Thanks in advance,
uberpixel

[Huffer]

My advice would be to put the car up on jackstands, or a lift, then run the car in all gears.

Then see what happens - slick road surfaces aren't exactly scientific, and it will help to see if any parts of the drivetrain aren't doing what they're supposed. Perhaps the rear diff has been disconnected?

[shazapple]

Our cars don't have limited slip diffs. I was stick on my driveway. Only my rear left tire would spin. What can you expect from the cheaper trim levels ;)

How does your car handle in a snowy parking lot? If you can fishtail it then you have your AWD working.

Check the fluid in the center differential, thats what controls the front rear power split

[StatGSR]

are you 100% sure that its even an AWD subaru? there was FWDs.

[uberpixel]

How does your car handle in a snowy parking lot? If you can fishtail it then you have your AWD working.

Check the fluid in the center differential, thats what controls the front rear power split

No fishtailing here. Just the front wheels spinning. I'll check the diff levels today and see if it's low.

Thanks

[uberpixel]

are you 100% sure that its even an AWD subaru? there was FWDs.

Funny you should say that... The AWD sticker is kinda peeling off of my rear window... I had the same thought a while back and took a look. It's AWD. I also have the original window sticker that indicates AWD.

Reasonable question though...

[Wiscon_Mark]

hmmm, I would say you're just slipping the front wheels because the 4EAT is FWD biased, although you did lock it in 1 and 2...hmmm, dutyC burned out maybe?

[Huffer]

No, dutyC burned out should result in a permanent 50/50 torque split.

Hmm. Maybe.
I might be getting mixed up between seized clutch packs and the duty c.
I had the problem with the seized clutch packs, and was locking up 50/50.

[uberpixel]

Check the fluid in the center differential, thats what controls the front rear power split

Maybe a dumb question - but - how do I identify the center differential. I see a front and a rear in the service book I have but I'm not sure about the center.

Thanks!

[Wiscon_Mark]

Center diff is in the transmission.

[jey]

Our cars don't have limited slip diffs. I was stick on my driveway. Only my rear left tire would spin. What can you expect from the cheaper trim levels ;)


The manual transmission versions of even the lowest trim have a limited slip center diff :)

[uberpixel]

Center diff is in the transmission.

How can I identify the check/fill plug for the center diff?

Thanks!

[Wiscon_Mark]

Jey, you know what he meant ;)

[Huffer]

Center diff is in the transmission.

How can I identify the check/fill plug for the center diff?

Thanks!

It's the same as the AT fill hole, and the AT drain plug.

[uberpixel]

Well - I put my Legacy on jackstands to get all 4 wheels off the ground so I could test the AWD. With all 4 in the air and the car in Drive the front tires spin but the rear tires do not. So that pretty much confirms my earlier observations that I am not getting any contribution from the rear wheels. (I also tried it in Reverse a la Ferris Bueller's Day Off - but the miles just wouldn't come off :wink: )

I was under the car and noticed that the tranny had some paint pen markings on it that said 90k. I'm guessing that it was either replaced or serviced at 90k. I bought it with 95k and the car is now at 150k. I suspect that I was ripped off when I bought the car - but that was a few years ago so I doubt that I have any recourse. I called the local Subaru dealer and he thought that the MPT (multi-plate transfer) clutch was bad. He quoted $1050 for a repair.

Does anyone know a good Subaru mechanic in Portland, OR???

I'm wondering if it could be anything simpler. It makes me think that maybe when the tranny was serviced at 90k it wasn't done correctly. I guess either way the standard fee for cracking open a transmission is $1000.

Anybody ever have thier MPT clutch go bad? Any other ideas?

Thanks!

[Wiscon_Mark]

PDX tuning is in Portland...

[uberpixel]

PDX tuning is in Portland...

Thanks. I'll give them a call.

I'm originally from Mad Town by the way. It was a tough place to leave...

[Wiscon_Mark]

I like mad town. Stevens Point is the next best thing though. Love this city.

[Huffer]

Anybody ever have thier MPT clutch go bad? Any other ideas?

If they go bad the car SHOULD end up locking up 50/50 torque split.
That's the first sign of trouble, is when the AT won't release the rear.

[Sarra]

Does your car have a tow mode? Check to make sure there isn't a fuse in the little thingy marked "FWD" or "Tow Mode" or whatever.

[Wiscon_Mark]

Does your car have a tow mode? Check to make sure there isn't a fuse in the little thingy marked "FWD" or "Tow Mode" or whatever.

Did you read the original post? He checked that.

[Sarra]

Does your car have a tow mode? Check to make sure there isn't a fuse in the little thingy marked "FWD" or "Tow Mode" or whatever.

Did you read the original post? He checked that.

I skimmed it. :(

Most of the suggested problems would cause CEL's, bad behavior, or other obvious signs, like whining, rattling, or huge "thunks" while driving.

Is there evidence of leaking fluid from the rear diff? I think having no fluid in the rear diff, or the wrong fluid, would cause it to not engage.

[Huffer]

Could it be a case of a relabeled VIN#?

[Wiscon_Mark]

Could it be a case of a relabeled VIN#?

Well, it'd be pretty obvious by looking if there was no AWD system.

[uberpixel]

Could it be a case of a relabeled VIN#?

Unless they went to the trouble of installing a dummy driveshaft and rear diff I don't think that's the case...

I was going to check and change the diff oil last weekend but I didn't have the right wrench to remove the plugs. What kind of wrench do I need? The plugs have a large square shaped depression. Is it just a large socket wrench size?

It seems to me that if it's possible to enable 2WD with a simple electronic switch (fuse in 2WD slot) that it would be possible for the tranny controller to get confused and lock up in that mode. My 2WD indicator works and only lights when I have the fuse in place so it doesn't seem like it's just a simple short in that circuit. I'm hoping that it could be something like that which would be cheaper and easier to fix as opposed to rebuilding the tranny but I really don't know.

Thanks!

[Wiscon_Mark]

I sincerely doubt that it just went into towing mode on a short circuit or something. The way of activating that is completing a circuit with a fuse - not the other way around, which makes it very unlikely that it's "confused"

did you happen to look underneath when you had it in gear? Was the driveshaft moving at all?

[Huffer]

I was going to check and change the diff oil last weekend but I didn't have the right wrench to remove the plugs. What kind of wrench do I need? The plugs have a large square shaped depression. Is it just a large socket wrench size?

half inch drive. All you need is a socket wrench.


It seems to me that if it's possible to disable 2WD with a simple electronic switch (fuse in 2WD slot) that it would be possible for the tranny controller to get confused and lock up in that mode. My 2WD indicator works and only lights when I have the fuse in place so it doesn't seem like it's just a simple short in that circuit. I'm hoping that it could be something like that which would be cheaper and easier to fix as opposed to rebuilding the tranny but I really don't know.

Thanks!

Incorrect. The FWD fuse slot when enabled (ie. fuse in fuse holder) ACTIVATES FWD mode. When the fuse is removed, normal operation of the transmission ie. 90/10 should occur.

[uberpixel]

Incorrect. The FWD fuse slot when enabled (ie. fuse in fuse holder) ACTIVATES FWD mode. When the fuse is removed, normal operation of the transmission ie. 90/10 should occur.

My bad - I meant to say "enable" not "disable". I've edited my original post.

Does anyone here know how the 2WD switch works? It seems that if the standard operation is 90/10 there must be a special mode that completely disengages the rear driveshaft.

Thanks!

[uberpixel]

did you happen to look underneath when you had it in gear? Was the driveshaft moving at all?

I was just thinking about that. I'll have to put it up again and take a look. Nothing like climbing under a car in gear on $16 jack stands... Sounds like fun!

[Sarra]

did you happen to look underneath when you had it in gear? Was the driveshaft moving at all?

I was just thinking about that. I'll have to put it up again and take a look. Nothing like climbing under a car in gear on $16 jack stands... Sounds like fun!

Take video too! :O

Okay, don't really, car + jackstands + gear = enough to deal with. :p

[legacy4ever]

uberpixel, have same problem as you... still unsolved :-( glad we have no snow in Europe this winter.

As far as I checked, electronics seems to be ok, tranny throws no codes. I measured the voltage and resistance of some tranny components with the multimeter on the main plug, they are all intact. (particulary duty C and duty B solenoids).

Been to dealership, they said duty C screwed, must replace (bull$hit, as Huffer said with inoperative duty C solenoid you get constant 50/50 torque split with shudder by cornering!).

I managed to get to a competent workshop, but they had no free place this time to dismantle the tranny, so they only changed the atf and filter. But there were many shavings in the oil pan, so there's something really wrong with the tranny (maybe the mpt clutch gone?). I had neither time nor opportunity to have it overhauled, so I put lubegard to the fresh atf and went on the trip. I hardly use the car now, cause it needs that transmission overhauled.

If you get your trans repaired, please let me know, what was the issue. thx