Thanks Mister Two,

I'm guessing plated LSDs are 'hellical'/mechanical?

And my MY00 WRX would have a 3.9 R160 viscous rear?

I am keen on fitting a LSD rear... there is one going cheap at the moment, but I want to be sure it's what I'm after.
Apparently it's off a 97 STi RA, and was fitted to an 04 WRX.
I know the V3 RA had R180 gear, so it cant be off that (unless he changed shafts and hubs), but the V2 had a R160 plated with DCCD...

I will have to check the bolt spacing to establish if it's R160 or R180... but is there any way I can check for viscous vs plated without opening it up?

The K bit does give you the ability to distinguish R180 from a MY01 onwards STi

And to spot the difference between R160 and R180 is put them side by side, one's bigger than the other

Plated LSD is NOT the same as a Torsen Helical.
Plate LSD uses clutch plates to lock up the LSD to give a stable 50/50 torque split between the left and right axle.
A Torsen Helical uses planetary gears to transfer more torque to the wheel with the most grip. (ie. the outside wheel in a corner)

Your my00 WRX comes standard with a 3.54 Viscous LSD rear Diff

If that diff came out of a 97 RA (WRX RA - not STI RA) and was fitted to a 04 WRX, then it is a 4.44 ratio.
The V2 STI came with a 4.11 Viscous LSD. ONLY the V2 STI-RA came with a 3.9 Plate LSD

__________________
RS Liberty - Because WRX's are only good for parts...

Suretrac is a torque sensing LSD, it only begins to lock when torque is applied, not when coasting, that makes it a one-way differential. And I can produce SUbaru technician literature that supports it.

__________________
Its just the internet dude, its not real.
F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i

Diff FS thread is here http://www.perth-wrx.com/vb/sale/40992-your-chance-bargain-lifetime.html

From his description it is a 3.9 from a STi RA, fitted by ASG to his 04 WRX.

Would this be bolt on for MY99/00?

It would be so much easier if I could find a chart of all this information, there is just so much variety and different combinations! :/

3.9 wont work in a MY99-00. These need 3.545 rear ratio. Or you could change the transfer gears from 1.1 to 1, to 1-1

__________________
Its just the internet dude, its not real.
F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i

Suretrac LSDs dont lock with more torque input. They bias to the wheel with the most grip.

__________________
RS Liberty - Because WRX's are only good for parts...

They only operate when torque is applied, thats what i said, to say they lock maybe is wrong, but essentially they are one way.

__________________
Its just the internet dude, its not real.
F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i

I've gone back over my technician reference books, Suretrac does lock, and it is mechanical, when there is a speed difference between the 2 wheels, it tries to equalize the speed, just like any other LSD.

__________________
Its just the internet dude, its not real.
F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i