Time to change diff oil.  I tow a 9,000 trailer most of the time.  Going to get magnetic plug.  Also any benefits of changing to Royal Purple 75w-140?  I believe it is Dana 70.  4.10 gearing. Limited slip. 

 

Thanks

Personally I would just run normal diff fluid. 

Limited slip requires 75w-140 synthetic. I would just get a local fluid and run it.