MzSquawk

Hi I have a Subaru impreza wrx 51 plate. (GDA,080).I went out the other day and ended up with a puncture. I put a space saver spare on and ever since have had an awfull judder from rear wheels when the car has warmed up and when turning. I have removed the spare and it has it's wheel bk on,still does it. I was told it was the diff which has now been replaced but is still doing it. Please help any ideas???