It is basically a 33/34 vspec rear end, The alsd is a bigger stronger diff than the gtst diff and uses gtr half shafts to boot. The only difference between the gtst and gtr alsd is the ratio. the gtst has 4.11 gearing and the gtr uses 3.9.
They can be troublesome when they start single spinning but regular bleeding of the hydraulic system keeps them working well. If bleeding it doesnt help I suggest you re shim it and try again. Failing that the clutch paks may need replacing.
I have read posts on here where people have not ben satisfied with them and changed the rear end out to standard gtst but i wouldnt swap mine out for quids.