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Old 09-19-2007, 06:11 PM   #1
BakedPotato
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1996 Legacy Outback

Default Help: AWD not working

I have a '96 Legacy Outback wagon with 153k. It's got an automatic and AWD. The rear wheels are not driving at all and in fact the driveshaft isn't even turning. There's no fuse in the "FWD only" slot and there's nothing that could be bridging the terminals and completing the circuit. There's no error message on the dash and a scan of the OBD doesn't yield any information.

Any ideas? We need those two extra wheels for our Jersey winters!
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Old 09-19-2007, 06:45 PM   #2
Bakergtt
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Sounds like you have a problem with your front dif or the tranny
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Old 09-19-2007, 07:49 PM   #3
legacypipedream
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probably your tranny
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Old 09-19-2007, 08:01 PM   #4
BakedPotato
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Where would I look first? The TCM? Is there a way to eliminate certain possibilites?
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Old 09-20-2007, 12:12 PM   #5
Wiscon_Mark
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It's probably a mechanical issue.

I would've said viscous coupler, but you have an automatic, obviously.
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Old 09-20-2007, 12:30 PM   #6
Huffer
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Default

Quote:
Originally Posted by BakedPotato View Post
I have a '96 Legacy Outback wagon with 153k. It's got an automatic and AWD. The rear wheels are not driving at all and in fact the driveshaft isn't even turning. There's no fuse in the "FWD only" slot and there's nothing that could be bridging the terminals and completing the circuit. There's no error message on the dash and a scan of the OBD doesn't yield any information.

Any ideas? We need those two extra wheels for our Jersey winters!
Are you in D or D3/D2?

D yields a 90/10 torque split and the rear wheels will typically only engage if the fronts are slipping.

D3/D2 brings a 60/40 torque split (thereabouts) and you should see the rear wheels turn if the car is on a lift.
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Old 09-20-2007, 01:55 PM   #7
BakedPotato
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On the lift, it's been in D, though I believe I've cycled through the other speeds with no result. The last time it rained, I drove around and floored it a few times to see if, as you said, the rears would engage when the fronts started to slip. All I got was front wheel spin and nothing from the back. The problem doesn't even come and go intermittently - the rear wheels are simply dead in the water.
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Old 09-20-2007, 02:13 PM   #8
Huffer
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Try it again on loose gravel/water in D3 or D2. If you can't go into a spin on throttle over then the rears are definitely dead.

In which case I would say there's a problem between the transmission and the rear transfer case?

??
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Old 09-20-2007, 03:06 PM   #9
BakedPotato
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Thanks for the advice, Huffer. I just tried what you said and the rear wheels are definitely completely out of the picture.

Any other advice (you've been massively helpful thus far)? Is it possibly that changing the ATF and diff oils would restore at least some function to the AWD system? Anything is worth a try at this point.
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Old 09-20-2007, 07:24 PM   #10
Huffer
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Honestly I think that if there's something mechanically wrong with the drivetrain, new fluids aren't going to help a great deal if there's literally no movement of the rear wheels.

If there's no CEL or AT light flashing, then the ECU thinks everything is A-OK.
At this point you've gone beyond my expertise...
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Old 09-20-2007, 08:58 PM   #11
BakedPotato
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I was just thinking along the lines of friction modifiers being too broken down or something, but that's probably far-fetched. Anyway, thanks again.
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Old 09-21-2007, 02:51 PM   #12
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Check the vaction pictures for that year. the auto trans uses a computer controlled clutch to engage the rear drive shaft to various degrees. The system is front drive based but you should still get some spin in the rear. If the wire or wires have are not connected to the clutch pack it will not engage and could go 100% front. The system has changed a bit over the years but the general functionality is the same, that is when you should check the pics for your year. The clutch pack could be dead but you should still be able to test voltage to it.

Hope that helps.

Peace,

Greg
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Old 09-21-2007, 04:31 PM   #13
BakedPotato
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Where can I find these pictures?
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Old 09-22-2007, 05:44 PM   #14
Jonathan
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Forgive me for speculating about a detail I don't understand.

Just how how is "slippage" detected ?

While I understand that some low-end AWD models (The Briton?) don't have ABS or even rear disc brakes, I have always assumed that those "gear teeth" tone rings on the CV axles were used to generate some sort of a "pulse" signal that gets compared between front and rear, and when there is an imbalance between the front and rear axle pulse signals, the electronically controlled clutch packs are activated.

Perhaps on your car there are no tone rings on the front CV axles or the tone rings are so badly rusted and/or corroded that they aren't generating a proper "pulse" signal ?

Maybe I am totally off-base here and Subaru uses an entirely different technique for measuring axle rotation ?

Last edited by Jonathan; 09-22-2007 at 05:51 PM.
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Old 09-22-2007, 05:50 PM   #15
Jonathan
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Oh and for what it is worth, on my '96 Subaru "L" sedan with AWD, ABS, and 4EAT Automatic transmission, I was only really aware of the AWD kicking in when driving in snow or ice.

I found that punching the throttle at low-speeds while cornering on limited traction surfaces, definately gave me a rear-bias on acceleration. The back end came out in what could best be described as a traditional "power-slide".

EDIT: Another thought... Have you tried driving in an empty parking lot, making very tight turns ?
Even at slow speeds you should detect an "imbalance" between the front and rear axles.

I first noticed this condition when making an illegal "U-Turn" on a hard surface public roadway.

Last edited by Jonathan; 09-22-2007 at 05:57 PM.
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Old 09-25-2007, 03:24 PM   #16
BakedPotato
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Default Fyi

I was at the local Sub'ru dealer yesterday and I described my problem to one of the techs. He said it sounds like the transfer clutches are worn and/or the solenoid controlling said clutches is malfunctioning/dead. He quoted roughly $1,000 for repairs. This would involve opening the rear of the transmission and replacing the clutch pack and solenoid.

Maybe we'll just go FWD from now on and throw some snow tires on for the winter months.
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Old 09-25-2007, 04:43 PM   #17
b4wantab
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Baked sorry I was busy the last few days. Do a search for "vacation pictures" or maybe someone will PM you with the page or two or three you need. I would assume the signal from the ECM is 0-10 VDC, but it could be 0-12. Either way you should be able to hook up a multi meter, drive around and see some voltage.

I would think the plug to the clutch packs would be at the rear of the trans somewhere.

Anyone done any work to their BD (it's a BD right?) and have any specifics here? There should be a way to test the signals before you have to crack it open.

Peace,

Greg
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Old 09-25-2007, 08:42 PM   #18
fastenova
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I have a 4eat from a BD sitting in my garage. I'll look tonight. I also have the FSM so I might be able to figure something out. I'll see what I can do.

-A
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