Limited Slip Diff.
 

I am purchasing a 97 Impreza Sport Wagon. I don't think they come with a Limited Slip Diff. I have heard that the WRX does but the WRX has a 3.90-1 and The Sport wagon has 4.11-1. What are my options?

What is the life expectancy of the clutch with normal, mostly Hwy driving?

Do you know of any week points I should be aware of?
Tom
[email]asg@ipass.net[/email][/EMAIL]

i think it is $800 to go to the dealer and ask for the WRX LSD and it should just bolt in

the clutch should last from 100k-150k mile for mostly highway maybe close to 200k

WRX does not have LSD
we have viscous differential
two different things

[QUOTE][i]Originally posted by nic3krnnamja83 [/i]
[B]WRX does not have LSD
we have viscous differential
two different things [/B][/QUOTE]

viscous differential IS LSD,
same system as AE86 GTS or 240SX SE, not strong but still an LSD.

WRX rear diff is 3.9 final and you need to swap the ring and pinion to make it 4.11.
However, automatic WRX one is 4.11 you can use this one.

or
00, 01 2.5RS has 4.11 viscous LSD, so if you find those, it'll just bolt on.
automatic 2.5RS is 4.44, cant use these.

i have always known it as two different things, cause they have two different names they may do the same thing in a sense but one is much better.

Any system for reducing wheel speed differential across an axle is considered a limited slip differential (as far as diff-mounted stuff, not traction control systems using the ABS). But yes, some are better than others, and different applications are better for different LSD types.

It wouldn't be too hard to find a 200-2001 RS rear diff in a recycler yard. Much simpler option than changing ring and pinion on a WRX diff.

This is really great Information! Thanks to you all for your assistance! I will expand on my LSD / viscous differential question. Does anyond know the slip resistance rate? At one time the factory LSD on BMW's was 25% and the racing unit was 75%. I have an 84 GTI that came with a 20 ft.lb. LSD and have upgraded it to 80 ft. lb. Is there any simular info about Subaru?

dont know about the specs but you can get various LSD for your purpose.

stock viscous is cheapest and least strong.
response is slow too.

there is gear type diff offered on Japanese models (suretrac)
response is faster and stronger than viscous.
a little bit hard to come by and a little more expensive

the strongest one is aftermarket clutch type diff.
pretty expensive. and needs a lot of attention (frequent oil change, overhaul clutches every year or two. etc.)
You can get pretty close to locking on these type diff.
If you make it strong, it'll suffer streetability because its hard to turn tight when you want to park..

Can anyone explain how the viscous diff. works?

[url]http://auto.howstuffworks.com/differential9.htm[/url]

There is a lot of information about differentials there.

Check out Kaaz, Quaife, Cusco, and cobb for more LSD. Basically, there are 3 different types. There is the viscous that works by heating a contained liguid which works similar to a torque converter inside the diff. There is also mechanical type which is as complicated as it gets and if one peaces fails then you are screwed but they do work very well. The most commn after market one is probably the clutch type which has numerous little clutch type discs that rub and transfer power. The only thing bad about that is that they need to be replaced periodically (the clutch disc do not the whole assembly). The most cost effictive is the WRX Viscous one.

the "new car" sticker states the WRX has a "limited slip differential"

All-Wheel Drive (AWD) Full-time AWD system automatically distributes power between front and rear wheels based on traction needs. Manual transmission models have a viscous-coupling locking center differential. Automatic transmission models have Variable Torque Distribution (VTD). VTD utilizes a planetary center differential in conjunction with an electronically managed continuously variable transfer clutch. WRX models have a viscous limited-slip rear differential

I've got an 03 2.RS. Would I only have to swap my stock ring and pinion to make the stock WRX rear differential LSD work?

Yes, or you could just get a complete RS diff from a '00-'01 model.