rear diff problem
 

right guys just fitted an sti version 5 gearbox and diff into my l reg wrx and both rear wheels seam to be figthing each other when turning as if it has a welded diff what could be the problem

Are you sure you've got the correct rear diff ratio for the box you've fitted?

yes diff and box came from same car and it is ok in a stright line and long bends it's just sharp bends it does it but one good thing is that i donughts alot better apart from it snaped a shaft today

Sounds like your viscous center diff isn't too happy. I have the same issue and a replacement waiting to go in but its not too bad and moved house so haven't got around to it.

Front and rear wheels travel at different speeds when turning corners and the viscous center diff is supposed to slip to allow this but they don't last long if you're keen on donuts.

The STi 5 should have a 4.44 diff front and rear with 1.0:1 drop gear.
First thing to do is drop the oil from the rear diff and remove the alloy diff cover.
Look for stampings on the outer edge of the crown wheel. Something like 40:9 ie 4.444.
Now check the pinion actually has 9 teeth.
A torch, rag and typex or similar makes the job easy.
Come back to me when you have done these checks if you want more assistance.