View Full Version : Subaru Diffs (please explain)

13-08-2006, 09:38 PM
Would anyone like to explain which subaru diffs fit s30s, the ratios they are available in, how to identify and modifications needed to get them to fit?

Only I've seen plenty of cheap ones on ebay but have no idea exactly whats needed. Hopefully this will be useful for others and not just me.



13-08-2006, 11:06 PM
I've bought a 4.11 viscous LSD from a scooby legacy estate 1990'ish.
Bolts up into place using moustache bar and front mount, just got to make some scooby/Dat drive shafts (good welder and a bit of NDT, stress relief, and balalnce jobs a good un) as the scoob inner is CV's on splines and i'm spicer's on my rear hubs. The slide (long/short motion) will be contained withing the scooby inner CV as this has around 1.5 inches of free float. When I'm doen will post up some pic's.
Next event end sept so times pressing.


14-08-2006, 12:40 AM
Perfect thanks.

14-08-2006, 12:51 AM
"All diffs were created equal"

To most people an LSD is an LSD... far from it

Viscous LSD diffs are considered "modest" performers when compared to either plate or torsen diffs, (much better than an open diff though)
Working by plates submerged in a "shear" fluid, viscous diffs relay on a differential in speed where as both plate diffs and torsen (especially) work on torque (real world)
Manufacturers like viscous as they are cheap to make (in comparison) and have few wearing parts however they have inherant limits as to what they can handle (power wise). Plate and torsen diffs however can be built to handle almost anything
I guess you gets what you pays for;)

Dont forget that Scoobys have 4 wheel drive so power gets shared out 4 ways (and weight to be moved) rather than the 2 ways (as in a zed) so 300 HP in a Scooby (approx STI spec) = 75 per wheel (assuming 50:50)
200hp in a Z = 100 per wheel or 25% more per drive shaft and more weight per axle to move :eek:

Due to the way they work (plates in a temperature reactive fluid) viscous diffs can take a split second longer to share the power out (the plates need to heat the fluid to provide a "shear" state and hence a reaction) than plate or torsen diffs so for a split second most of your power can be going one way

so just make sure those shafts are good and strong ;)

On the plus side it will entitle you to have your wheels sprayed gold and to hang around in McDonalds car parks:D