Quote Originally Posted by tbplus10 View Post
Check the rear brakes before you open up the diff, not unheard of for a set of shoes to break loose and cause this type issue.
It is fixed! Should have done this first and saved my friend's money from spending on rear diff gear oil and gasket. Came to find out there was a bolt that broke loose in the rear park brake that was causing the rear wheels to lock up once in a while. Sometimes, it will drive fine and just lock up for no reason.