I had a shop change my rear end fluid recently. They added High Performance Valvoline 80w-90 GL-5 LS gear oil. It says it's specially formulated for limited slip, high horse/torque power applications. The mechanic said with this fluid I did not need the GM limited slip additive. I don't know how true this is, should i add it myself or will i be ok? I have the same Auburn High Perf Diff That was installed in the Firehawk and SS cars. Any suggetions?
__________________

 

You need the additive.

Rich