Gearbox or Diff

HI,having trouble with a WRX impreza [96].When in reverse its very noisey,all other gears are fine,if you were turning the car an a street or outside the house it gets hard move off as if the brakes were sticking[have checked brakes]when your taking a corner at 50,60mph the arse of the car is mad to diff out,also when checking the brakes i noticed all four wheels are tight [maybe this is normal].Taugh myself it must be the box but another lad told me it could be a diff.but which diff,Any way of finding out before i buy parts.Thanks.

wen you turn in a circle does the inside wheel could look if diff is KO'd.

Sounds like a very tight rear diff, would need to have a look at it on a ramp

John