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Old 08-17-2008, 09:30 PM   #1 (permalink)
Legionairre

 
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Default 99 Outback difficult to slide on slick surfaces

I have a 99 outback with the 4EAT and have an annoying issue. I do NOT have a rear LSD and notice that the rear differential tends to diff out easily. For example on a slick surface such as sandy rocky dirt on the road I can feel the inner rear tire spinning and the outside doing nothing. I feel as if it is time for a rear fluid change but am having difficulty getting the fill/ drain plugs off.

My question is would new and possibly slightly thicker gear oil slow down the action of the rear differential?

Also today to check the AWD system I pulled up a not so steep grassy hill as to test the AWD.

From a stop I noticed the front right wheel seemed to spin the most with no slippage in rear. It appears that the front gets the majority of the torque even when put in gear 1. (I understand how the AWD system in the 4EAT works). I tried putting a fuse in the FWD holder under the hood to see if the rear was even doing anything and the results were more obvious. The front right would spin even more. Even under generous applications of the throttle with the intention of getting the rear to spin, it would NOT- only the front.

I would like to get more torque to the rear tires if possible and prevent the front and rear open differentials from slipping so easily. I was planning on putting in 80w gear oil in the front and rear diffs, but not sure what to do about the center clutch pack. Any possible ideas or flaws with my logic?

Lastly my reason for doing this is that winter is approaching in a few months and I would like to have my AWD system working well. Thanks!
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Old 08-18-2008, 02:30 AM   #2 (permalink)
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i read that twice and i still don't know what you are asking ?

putting a fuse in the holder defeats the awd and causes the rear wheels to get no power.

open diffs will allow one wheel to spin while other does nothing, that's what "open diff means" lsd is limited slip which reduces but does not eliminate this, lockers are the only thing that cause total lockup.

thicker fluid will not make your wheels get more power delivered to them.

you should have one front and one rear wheel getting power at all times, when the front starts spinning the rear should get power immediately.
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Old 08-18-2008, 05:30 PM   #3 (permalink)
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Quote:
Originally posted by ETC
i read that twice and i still don't know what you are asking ?

putting a fuse in the holder defeats the awd and causes the rear wheels to get no power.

open diffs will allow one wheel to spin while other does nothing, that's what "open diff means" lsd is limited slip which reduces but does not eliminate this, lockers are the only thing that cause total lockup.

thicker fluid will not make your wheels get more power delivered to them.

you should have one front and one rear wheel getting power at all times, when the front starts spinning the rear should get power immediately.
I understand how differentials work maybe you misunderstood me.

I put the fuse in the FWD holder to purposely lock it in FWD so I could see if the AWD system was even working with the fuse OUT. The verdict was that while the AWD worked, it wouldn't transfer much torque at all to the rear wheels.

In reference to differentials an open diff becomes looser with use. A new differential will not diff out as easily as one that is 10 years old. Correct me if I am wrong but doesn't the viscosity of the fluid change the dynamics of it's action? Thereby thicker fluid produces more friction preventing the tendency to "diff out"?

I understand this vehicle does not have lockers nor any LSD (center clutch excluded) but compared to how this car use to feel, it feels as if the diffs may be burning or worn out. My question is would old fluid make this problem worse?

by "diff out" I am refering to one wheel on the same axle spinning while the other remains stationary.


My problem is that now the car feels heavily front wheel drive with a marginal rear wheel assist. I understand the 90/10 to 50/50 in the 4eat and I am not getting anywhere near 50% to the rear wheels what so ever.
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Old 08-18-2008, 05:41 PM   #4 (permalink)
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The action of the rear diff that you describe, where it doesn't "diff out" as easily when new, is news to me. There is nothing in an open differential to maintain traction to both wheels, so there is no reason for that to change. "Diffing out" as you call has everything to do with your traction to the surface you are on, and nothing else. Only way to help that his with new tires or weight distribution. . .that sort of thing.

What you described is more typical with a VLSDs they put in these cars from 2000 up. The VLSD works fairly well when it is new, but as the fluid is overheated it becomes less and less effective. Viscous couplings rely on a silicone fluid that changes viscosity with temperature, so that when the plates in the coupling are not turning at the same rate, the fluid becomes more viscous and helps to transfer power. The gear oil that is used in the rear differential on an LSD is for lubrication only, and has no interaction with the silicone fluid and viscous discs.

It sounds to me more like you are not getting the amount of torque transfer to the rear end that you would like, which would imply issues with the center differential, not the rear. So it seems like that is where you focus should be, along with getting a set of tires that are going to give you better traction on the two wheels that are getting power.
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Old 08-18-2008, 05:45 PM   #5 (permalink)
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Understandable and thanks for the quick reply.

I did purchase a new set of tires a few months ago so that is not the issue.

I havn't been able to nail down the exact location of the problem but starting to put money on the center diff. I wasn't sure if maybe the rear diff was blown thereby when the duty c solenoid sends more torque to the rear, it just helplessly spins which ever tire has less traction, giving the illusion that the rear isn't getting torque. This is really frustrating, it simply feels like the car is front wheel drive...
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Old 08-18-2008, 05:54 PM   #6 (permalink)
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I had both a 1996 and 1998 Outback, so I know the sensation you are feeling. But I went through a couple of MT winters and had absolutely NO issues getting where I wanted to go, and this included plowing through 18" powder and 6" of wet slush at times. I think what you are feeling is pretty normal, it is really hard to tell what the wheels are doing when you are inside the car, and it is impossible to know how much torque is transferred.

As I am sure you know, in 1st there is supposed to be a 50/50 torque split, but one thing about putting the car in 1st or 2nd is the fact that the clutches in the transmission are allowed to slip more, in an effort to make it harder to spin the wheels, which could be adding to this effect. It makes the accelerator feel like it is connected to the throttle by a rubber band.

Truthfully, you aren't really going to know how it will perform until you get it into the snow, and I have a feeling that it will do just fine.
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Old 08-18-2008, 06:03 PM   #7 (permalink)
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I've had this car for 6 years and driven in plenty of winters. Last winter I had a really worn set of tires that were almost bald, in the snow I could initiate on power oversteer pretty much on demand. Around January I bought a set of Blizzak studless snow tires. On the snow I can feel the same issue. The fronts spin and the rear doesn't get much torque making it frustrating. I never get stuck but I feel as if the car is not what it used to be like. With the Blizzaks on it understeers horribly on power. Maybe it was simply the bald tires gave the illusion of giving more torque to the rear...
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Old 08-18-2008, 06:07 PM   #8 (permalink)
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Your car does not have limited slip differentials in the front and rear axles.

What you are seeing is normal. The car can only do so much to make up for an overly enthusiatic driver. What you are seeing is normal.


Normally when the tire starts to spin, you back off the gas.

I suggets you try this.

The only way you have any inputy in getting more torque to the rear wheels is by putting the car in low gear. The AWD computer will be more agressive in supplying torque to the rear wheels, but is still will only put in as much as is required to get the car to move.

Sounds like to me you want a subaru to behave like a jeep, which it is not.

Also gear oil has nothing to do with this, but tires do. A more agressive tire pattern will aid in traction.

If you truly truly get stuck with one wheel spinning on both axles, a light application of the parking brake or the service brake will transfer power to the non slipping wheels, but this takes practice.

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Old 08-18-2008, 06:09 PM   #9 (permalink)
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Also this makes no sense at all...

In gear "1" with the supposed 50/50 split I can NOT get it to oversteer on power yet in 2nd I am able to....

This is on the snow by the way.

The reason why I care so much is I find cars that understeer this badly in adverse conditions can be very dangerous and in slippery conditions such as snow, ice and wet grass, suspension has very little to do with it. I simply want more neutral handling in the snow. I have been driving this car for quite some time and am very comfortable with it sideways, especially in the snow. (TONS of practice in open parking lots over the years).

Hate to say it but maybe this car is just done...
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Old 08-18-2008, 06:11 PM   #10 (permalink)
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ok im bowing out of this one, as i dont think the issue is the car.

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