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2000 Forester
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Discussion Starter #1
2000 Forester Manual.

So my transmission was making some noise. It wasn't having trouble shifting or staying in gear, just noise. It has been roughly a constant level of noise for about 1 year now.

I took it to a 'subaru specialist' mechanic and they added some limited slip additive to my transmission fluid to help with the noise. I grilled them on it before adding it if it was some snake oil, if LS additive is okay in our trannys, and they assured me that it was fine to put in there.

After a couple of weeks, my wheels began to jump a little bit when turning very sharply like it was an old 4x4 where all the wheels spin @ the same speed. Then today I was backing into a parking spot and felt a large clunk, and thought I had killed the engine, but the engine was still going--- the transmission was just behaving strangely.

Now, I hear a knocking noise while driving forward, regardless of whether the the clutch is engaged or not and what gear its in. I don't believe it to be engine-related because it only knocks while the car is moving.

SO, any ideas on what the problem is? Also, what are the chances that the LS additive contributed/caused this issue?

If it comes down to a tranny rebuild/swap, what kind of general price range am I looking at?

Thanks, folks.
 

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LS additive shouldn't be used in the trans. Its designed for clutch type limited slip diffs like the rear diff in certain years of the STI.

How much mileage on the car? The clunk could be something unrelated. Possibly an axle/cv due to the added stress of the center diff binding (the hopping you had). Or even a diff or trans mount.
 

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2008 Forester X Premium 5MT
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8,070 Posts
Sounds like your already tired transmission is giving up ...
Agreed,

....After a couple of weeks, my wheels began to jump a little bit when turning very sharply like it was an old 4x4 where all the wheels spin @ the same speed. ......

This has all the symptoms of a center diff that has seized up, common as they age.

I would highly doubt that the LS additive had any affects on the failing of the center diff. It is a sealed viscous coupler. It could be in water and should still function. The additive may affect synchro engagement but should have little affect on every thing else.

As for the other sounds from the trans I agree with funkymonkey, they may be a result of the center diff binding.
 

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2000 Forester
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Discussion Starter #5
Okay. So is the solution to this pretty much a tranny rebuild/swap? How much should I expect to pay for such work?
 

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2008 Forester X Premium 5MT
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Before condemning it to a rebuild, try and have the noises diagnosed.

If they are from the axles,as a result of the seized center diff. I would replaced the center diff, IIRC the center diff can be replaced with the trans still in the car and only requires minor disassembly.

As far as what you are going to pay? There is no good way to give you a quote:
Rates vary by shop and region.
 

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2000 Forester
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49 Posts
Discussion Starter #7
Yeah, its definitely going into the shop for this one. I just wanted to be prepared for worse case scenario.
 

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04 Forester X, MT
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Before condemning it to a rebuild, try and have the noises diagnosed.

If they are from the axles,as a result of the seized center diff. I would replaced the center diff, IIRC the center diff can be replaced with the trans still in the car and only requires minor disassembly.

As far as what you are going to pay? There is no good way to give you a quote:
Rates vary by shop and region.
+1

and get the LS additive out of the tranny, it doesn't belong in there! replace it with a good quality (non LS) 75w90 gear oil.
 

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2000 Forester
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Discussion Starter #10
Before condemning it to a rebuild, try and have the noises diagnosed.

If they are from the axles,as a result of the seized center diff. I would replaced the center diff, IIRC the center diff can be replaced with the trans still in the car and only requires minor disassembly.

As far as what you are going to pay? There is no good way to give you a quote:
Rates vary by shop and region.
So pardon my lack of knowledge about the Subie transmission, but does it have a center diff + front diff + rear diff + viscous coupling, or what all part do I have distributing the power to my wheels?

I took it to a mechanic and they said it needs a new transmission. Very sad and very expensive. It's just strange because it goes through all the gears smoothly.

Also, the knocking noise is less when under acceleration. When coasting it seems to be louder.
 

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04 Forester X, MT
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So pardon my lack of knowledge about the Subie transmission, but does it have a center diff + front diff + rear diff + viscous coupling, or what all part do I have distributing the power to my wheels?

I took it to a mechanic and they said it needs a new transmission. Very sad and very expensive. It's just strange because it goes through all the gears smoothly.

Also, the knocking noise is less when under acceleration. When coasting it seems to be louder.
on MTs the front diff is inside the lower front part of the transmission and is really integral to the design.

the "center diff" is in the rear part of the transmission and can be changed without pulling the transmission out of the car.

the rear diff is at the back in-between the rear axles and has the driveshaft bolted to the front of it.


edit: re-read some posts, you need to find a knowledgeable shop that knows how to replace the center diff without pulling tranny and go from there.
 

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Discussion Starter #12
Unfortunately, I didn't get much explanation other than the transmission needing replaced/swapped.

So what is the deal with the VC, how does that factor into the whole equation?

One more symptom to add to the mix--- the car behaves the worst in reverse. It seems that it is best while under accel. forward, noisier while coasting, and has large shuddering while in reverse. Yet, the gears seem to shift smoothly, not pop in and out of gears.
 

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2002 Forester S
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270 Posts
Noooooooooooooooooooooo!!!!!

Do not put LS additive in the manual transmission!!!!! The friction modifiers will mess up the working of the synchros.

The 5MT shares oil with the front hypoid differential. MTs usually want a GL4, hypoids always want a GL5. When they share, hypoid wins and you MUST use a GL5. However, you do not want a GL5 with LS friction modifiers because of the synchros. Most GL5s have LS friction modifiers, so you have to find one which does NOT. Motul Gear 300, Neo and Redline NS do not have them. I'd say drain out whatever is in there now and replace with one of the non-LS modified GL5s like mentioned. At least then you'd have the correct oil in the thing.
 

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2010 Forester 2.5X
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^^^ what he said.
You haven't said if you got the oil out with the LS friction modifier.
Did you? LS modifier is a No-no in the transmission.
 

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Any mechanic who would put LS modifiers in a Subie 5MT obviously doesn't know jack squat about Subarus, and you should find a mechanic who does know these things.

LS modified oils work fine in the rear differential, and in the front differential of Subies with auto trannys. But NEVER in the 5MT. Wife's Foz has the 4EAT, and I used M1 oil in both diffs, it has LS mods. I also put it in the rear of my Outback. I'm running the cocktail in my 5MT.
 
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