Hi, I'm new to Foresters and have a problem with the rear differential on mine which is a 99 manual 2.0 litre GLS. The previous owner, for some reason, put an Impreza sti limited slip diff in the rear. This is very noisy now so I bought what was supposed to be a secondhand  4.111 manual diff and the garage says it wont fit because the splines are different. Are the drive shaft splines different on an Impreza? 
  
thanks 
  
Dave