I pulled a limited slip from a mustang 7.5 rear diff from the junk yard for $28. I want to install the limited slip in my mustang so I can race in a month. I know the 7.5 diff is weak but its what I have and money is tight. The limited slip only has one shim and its on the passenger side spider gear. I thought there was suppose to be more. All the spider gears seem to be aligned well and move freely. Is there suppose to be more shims? Or just one shim?