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- - AWD question (https://www.subaru-svx.net/forum/showthread.php?t=56137)

jeffs92svx

12-14-2010 04:57 AM

AWD question

I dont know anything about our awd system. This morning me and the wife were out in the snow. I have pretty much bald all season tires on the svx. Amazingly it comes out of my drive way and up my huge hill and it is slick. My question is, I had my wife to stomp it while I watched in the walmart parking lot and the two drivers side wheels spin but only the front passengers side spins. Does anyone know if all 4 are supposed to spin. We dont it a couple of times and the same results, the back passenger side wouldnt spin. Thanks.

Manarius

12-14-2010 06:47 AM

Re: AWD question

It should be the other way around: One in the front should spin while both in the back should spin.

The front differential is open, so the one with the least resistance is going to spin. The rear differential is LSD, so after a little bit of one spinning, they both should start to spin.

Also, if you have nearly bald all-season tires I wouldn't expect your car to be going much of anywhere. AWD is good, but bad tires make AWD worthless. You might as well be driving a FWD car with bald tires.

jeffs92svx

12-14-2010 03:30 PM

Re: AWD question

Actually it went really good. I dont know whey but both front and the drivers side rear spins and that it. Anyone else know of anything it could be or if it is normal.

92 SVX

12-14-2010 04:31 PM

Re: AWD question

Quote:

Originally Posted by jeffs92svx (Post 664651)

Actually it went really good. I dont know whey but both front and the drivers side rear spins and that it. Anyone else know of anything it could be or if it is normal.

the reason the rear might not be locking is something wrong inside the rear diff.
these are not mechanical limited slip diffs. the oil used might be gone or bad. I think they also use clutch disks and if they are toasted that might do it.

1986nate

12-15-2010 05:20 AM

Re: AWD question

read the next post by me as I wasn't thinking clear when i typed this one out :lol: :o

jeffs92svx

12-15-2010 06:18 AM

Re: AWD question

Quote:

Originally Posted by 1986nate (Post 664682)

The rear LSD inside the rear diff is mechanical. The transfer clutch in the transfer that controls power going to the rear is adjusted by the amount of throttle, slip from the front tires, etc but he has 1 tire in the rear spinning, meaning the rear is getting power.

So, is that the way it is suppose to be.

1986nate

12-15-2010 06:33 AM

Re: AWD question

Quote:

Originally Posted by jeffs92svx (Post 664689)

So, is that the way it is suppose to be.

It's hard to say if I take what you're saying correctly...

Basically, Open differential means that the power goes to whatever wheel has the least restriction (traction) on it.

-So if one wheel is on ice, and the other on dry pavement, only the tire that is on the ice will get traction

LSD which stands for limited slip differential should apply power to the wheel that has the most traction and if a wheel is slipping, will transfer the power away from that wheel to the other. So it is possible for one of the rear tires to spin depending on how slippery the surface is.

-So, again, one wheel on ice and the other on dry pavement, it will probably put a little bit of power to the wheel on ice before transferring all power to the wheel on dry pavement. So, the tire on ice could get enough power to spin it, and then because its on ice, there is no traction to stop it from spinning giving the allusion that it is spinning.

So disregard most of my previous post as I was not thinking clearly:o

92 SVX

12-15-2010 02:05 PM

Re: AWD question

Quote:

Oh, and a viscous LSD is driven by a viscous fluid. The two halfshafts aren't directly connected, instead they have fan-type things inside this viscous fluid, when the two wheels are spinning the same speed, both the fans and the fluid are all spinning together. When one wheel starts to spin faster than the other, it creates an imbalance in the LSD, the slower wheel wants to speed up and the faster wheel wants to slow down because of the fluid. On a hard launch you won't be able to tell any different between a car with an open differential and one with a viscous lsd until one wheel breaks loose, on the viscous car the power will transfer to the wheel that isn't spinning as fast, and on the open differential that one wheel will just keep on spinning how it wishes.

A helical LSD is gear driven, but I don't know the details. You can check on www.howstuffworks.com to find out the specifics of that. Basically both cars will act like they have an open differential until one tire starts to spin faster than the other, then the LSD transfers power to the other wheel. Same basic principle and feel, they just do it in different ways.

This is what I found on our diff with a quick search.

jeffs92svx

12-18-2010 05:02 AM

Re: AWD question

Sorry I'm not getting this guys. So, does our rearend have fluid that truns the axles? How do you replace the fluid? I am usually very mechanically inclined, I just dont know squat about this awd system. I have a thumping coming from the back to which kind of sounds like that wheel may be trying to kick in. How do I check the fluid level. Sorry guys, any help is appreciated.

svxfiles

12-18-2010 11:41 AM

Re: AWD question

Quote:

Originally Posted by jeffs92svx (Post 664873)

Sorry I'm not getting this guys.
1)So, does our rearend have fluid that truns the axles?
2)How do you replace the fluid?
3) How do I check the fluid level.

1) There is a 70/90 gear oil in the rear differential'
The LSD is sealed for life, needs no servicing!
2) There are two 1/2" drive plugs on the back of the rear differential.
Unscrew them and drain it.
3) When you refill it you use the top hole.
When the oil spills out of it while filling it, its full.

jeffs92svx

12-18-2010 03:25 PM

Re: AWD question

Thanks tom.

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