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96 Legacy LS Wagon w/ rear/center differential problems


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6 weeks ago we bought a 1996 Legacy LS wagon w/ 186,000 miles on it. When we bought it, it had the AWD disabled (by inserting the fuse in the eng. compartment).

 

After I learned about the fuse, I removed it, and we have driven it quite a bit in the AWD mode. We have noticed a definite "shudder" or binding when turning at slow speeds. The dealer explained that the rear/center differential needs to be fixed at $1000-1300.

 

Three questions:

1) Can we simply leave the FWD engaged (by re-inserting the circuit breaker) until we have money to make the repair? Or will that cause other damage over a long period of time?

 

2) Either way, does it cause any additional complications by waiting to fix this? Or can I simply wait till it totally goes out?

 

3) What exactly is the problem, and how much show I expect to pay at a competent, non-dealer shop?

 

Thanks!

Jim

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1000 is about right for the job. The FWD fuse is NOT meant for regular driving. IMO, you should get the job fixed now because if the transmission needs fixed and there are bits floating around in there, using the FWD fuse isn't going to keep those bits from getting circulated and you could potentially completely destroy your transmission instead of just needing the clutchpacks replaced.

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The rear wheels are driven through a wet-clutch pack in the back housing of the transmission, and this pack requires fluid pressure to engage and connect your rear wheels to power. "Engaged" is the normal state of this clutch pack with the engine running. There is a Transmission Control Unit (TCU) controlled valve (Solenoid Duty "C") that releases fluid pressure to this clutch pack when activated, removing drive power to the rear wheels. The FWD fuse bypasses TCU control and supplies constant activation to the solenoid.

 

The common failures seem to be: Failed solenoid, gummed-up clutch pack components (so they stick together and don't release), and damaged clutch-pack that is "welded" together. Some overlap of these problems, and different degrees of involvement.

 

If the FWD fuse works, probably just gummed-up components, possibly with some scarring of the clutch pack plates. The dealer is probably planning on replacing the clutch pack and the solenoid.

 

Possible damage? Energizing the solenoid could shorten its life, and when it fails (or the TCU THINKS it has failed) you will be locked in 4WD. (Bad failure mode IMHO.)

 

I have just begun to personally explore this problem, so others could give you better, first-hand advice. If it were me, I would try a couple transmission fluid changes first, probably with a tranny-cleaner like SeaFoam added to help clean things up.

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Very interesting. It really sounds like I should probably just go ahead and get it fixed right sooner rather than later.

 

I might go ahead and get the tranny fluid changed, if that doesn't do it, I'll be heading to the dealer real soon.

 

Thanks for your help, folks. If anyone else has any thoughts or anything to add, I'd really appreciate it.

 

Thanks a bunch,

Jim

 

Another thought, when I had my mechanic check out the car before I bought it, he thought the original tranny fluid may still be in there... all the more reason to get it changed, and prehaps part of the culprit of the problem.

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You've got torque bind, which has nothing to do with the differentials. It's caused by gummed up transfer clutches in the tranny, as explained above. I'd be wary of this dealer. They're blowing hot air. Try changing the transmission fluid, (one of those $99 flushes is probably in order) then driving in some tight circles. If it goes away, great! If it doesn't, prepare to empty your pocketbook.

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Flush the fluid first, after you make sure all the tires are the same size and inflated properly. a fluid flush is a gamble of 100.00 vs 850 (what i paid two months ago). i did the flush last year then the solenoid failed the other month, so had to get mine rebuilt.

 

nipper

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Follow Nipper's recommendations. The two key things to do are 1) check that the tires are inflated to the same pressure, and that they are the same circumference, and 2) Flush the tranny fluid completely... not just a partial change, make sure that all the old fluid gets exchanged for new.

 

I have quite a bit of experience with this particular issue, as it happened to my '96 OBW at about the same mileage. If you search for postings by me over the past 2 years or so, you will see that running in FWD mode via the fuse is NOT the danger that some people think it is. The solenoid is continually energized in FWD mode, but it is energized about 50% of the time in regular AWD operation, so if you have clean, fresh fluid in the tranny and if you aren't driving in extreme hot conditions, you can drive for months (years, even, heh-heh) without doing damage to the solenoid.

 

But the problem may go away with a simple change of tire pressure and fluid. Try those first, and do the tight figure eights recommended by another poster here. What you'll be doing, if it works for you, is freeing up the stuck plates in your clutch pack, and that will restore normal AWD without the torque bind being present.

 

However if the original owner tried all these tricks before you, you will likely have to get a new extension housing/clutch pack assembly put onto the back end of the tranny. They do cost between $750 and $1400 (depending on where you go to have the work done). WHen I was in Southern California and went out for quotes to have it done, I was quoted over $2000 by one dealer! I ended up buying a used extension housing/clutch pack from someone else on this forum, and put that on my old tranny myself. One weekend's work, and about $40 invested in the used clutch pack, including the cost to have it shipped to me, and my torque bind problem was solved. You might investigate sources of "used" parts. It can save you significant $$. My replacement "used" clutch pack is going strong after about 30,000 additional miles put on it by me.

 

BTW - I drove in FWD mode for nearly 2 years, before my solenoid finally gave up the ghost and I was forced to make the full clutch pack repair. Nothing says that you won't have a similar experience, if you choose to wait a bit before making the fix. You will do NO damage to the rest of the tranny by dleaving the FWD fuse in there for the time being.

 

Good luck!

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[...]We have noticed a definite "shudder" or binding when turning at slow speeds. The dealer explained that the rear/center differential needs to be fixed at $1000-1300.[...]

It's key to check the tires' circumference, as others have already suggested, because a significant enough difference between them can be the cause of the problem. See: http://www.endwrench.com/pdf/drivetrain/RearAxleBindingInfoF99.pdf

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It's key to check the tires' circumference, as others have already suggested, because a significant enough difference between them can be the cause of the problem. See: http://www.endwrench.com/pdf/drivetrain/RearAxleBindingInfoF99.pdf

 

 

Wow, thanks for posting that service bulletin. I had heard about that, but figured if the tires were the same manufacturer & basic size it would be good enough.

 

I know the front tires and rear tires are different manufacturers, could that matter? Or is it simply the "matching" tires (i.e. rear tires) that need to be the same manufacturer.

 

Jim

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Flush the Tranny and differentials, get 4 new tires and be on your way. Look at it this way, your going to have to get 4 new tires anyway. I also had a dealership tell me that I needed the same work done to my 95 legacy with 133,000 miles, only to find out by a honest dealership that by flushing the tranny and differentials would take care of it. IT DID. I sold the car with 210,000miles. Do the small things first, its only $100-150 bucks, much cheaper than $1200 they want for their work.

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Well, I had the four tires replaced. It may have helped a bit, but it definitely didn't solve the problem. But, just like you guys are saying, I figured that it needed to be done anyways to protect the system from further damage. The front and back tires were different brands; the front tires also were nearly new and rear tires at about mid-life or a little worse.

 

So it needed to be done, but I'll be heading off today to get the tranny flushed/cleaned. I'll post when I find out the results.

 

Thanks for everyone's input. Its great to be able to bounce this around with other people who have had subarus with the same problem.

 

 

Also, just to make sure I'm understanding everyone correctly, the clutch packs that need to be replaced are in the automatic transmission housing (NOT the rear differential), even though it is the rear wheels that are binding?

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The rear wheels are driven through a wet-clutch pack in the back housing of the transmission, and this pack requires fluid pressure to engage and connect your rear wheels to power. "Engaged" is the normal state of this clutch pack with the engine running. There is a Transmission Control Unit (TCU) controlled valve (Solenoid Duty "C") that releases fluid pressure to this clutch pack when activated, removing drive power to the rear wheels. The FWD fuse bypasses TCU control and supplies constant activation to the solenoid.

 

 

After looking over NorthWet's post again, I guess that answers my question in the affirmative... Let me know if I'm wrong.

 

By the way, NorthWet, great explanation, you seem to really know your stuff.

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Great news everyone! I got the tranny flushed and it looks like after my initial "test drive" that the problem is SIGNIFICANTLY BETTER.

 

So the dealer quoted me $1000-1300.

 

My costs:

 

$380 for new tires

$87 for tranny flush

 

TOTAL COST: $460-470

TOTAL SAVINGS: up to $830!!!

 

Thanks everyone for your help and for saving my family literally hundreds of dollars. I had asked two mechanics who I really trust about this, and they didn't know what to do (neither had much subaru experience).

 

Hopefully that's the end of it! :)

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Great news everyone! I got the tranny flushed and it looks like after my initial "test drive" that the problem is SIGNIFICANTLY BETTER.

 

So the dealer quoted me $1000-1300.

 

My costs:

 

$380 for new tires

$87 for tranny flush

 

TOTAL COST: $460-470

TOTAL SAVINGS: up to $830!!!

 

Thanks everyone for your help and for saving my family literally hundreds of dollars. I had asked two mechanics who I really trust about this, and they didn't know what to do (neither had much subaru experience).

 

Hopefully that's the end of it! :)

 

AWSOME!!! o and if there is a little tiny tiny bit off binding, change the rdiff fluids and it should be smoother than ever.

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AWSOME!!! o and if there is a little tiny tiny bit off binding, change the rdiff fluids and it should be smoother than ever.

 

 

Rear differential fluidS, plural? You mean just the one rear differential correct?

 

Before posting I had already tried changing the rear differential fluid, but to no avail...

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Now just keep an ear on things for the next month. If you make it through the month, then your golden

 

For the record there are two vlaves in the tranny, one is a spool valve, which we cant get to, the other is the Duty C Solenoid, which we can. The Solenoid controls the torque split by cycling on and off very quickly. The other valve regulates how much pressure is applies to the clutch packs. This allows for more slippage at low speed, and less at high speed.

 

nipper

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Now just keep an ear on things for the next month. If you make it through the month, then your golden

 

For the record there are two vlaves in the tranny, one is a spool valve, which we cant get to, the other is the Duty C Solenoid, which we can. The Solenoid controls the torque split by cycling on and off very quickly. The other valve regulates how much pressure is applies to the clutch packs. This allows for more slippage at low speed, and less at high speed.

 

nipper

 

 

Thanks Nipper, Subarus definitely are a little bit different of a beast.

 

Well, after driving it for a day I would say it is about 90-95% better! Every so often we get a little shudder, but nothing major. I'll keep an eye on it for the next month (well... as long as I have the car ;) ). But I'm very pleased and will probably leave it the way it is, assuming it doesn't get worse.

 

If it does, I may try flushing it a second time (as someone else has previously recommended).

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  • 10 months later...
Thanks Nipper, Subarus definitely are a little bit different of a beast.

 

Well, after driving it for a day I would say it is about 90-95% better! Every so often we get a little shudder, but nothing major. I'll keep an eye on it for the next month (well... as long as I have the car ;) ). But I'm very pleased and will probably leave it the way it is, assuming it doesn't get worse.

 

If it does, I may try flushing it a second time (as someone else has previously recommended).

 

For anyone who may be reading this post as a reference, it has been 10 months and over 10,000 miles later, and the car is still doing well. No major shudder to speak of (still a little bit on real slow, tight turns, but I never did flush it a second time). Flushing the tranny clean did the trick.

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AWD depending upon the sophistication (and subarus are very sophistaced) will always feel a little tight when you first start making a tight turn. Blu does that when you first cut the wheel tight, then the puters figure out what your doing, and it releases. The problem is when it doesnt release becuase things are gummed or or stuck..

 

 

nipper

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